Resist composition and method for producing resist pattern

ABSTRACT

A resist composition having a resin having a structural unit represented by the formula (I), a resin being insoluble or poorly soluble in alkali aqueous solution, but becoming soluble in an alkali aqueous solution by the action of an acid and not including the structural unit represented by the formula (I), and an acid generator represented by the formula (II), 
     
       
         
         
             
             
         
       
         
         
           
             wherein R 1 , A 1 , A 13 , A 14 , X 12 , R 23 , R 24 , R 25 , X 21  and Z 1+  are defined in the specification.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Application No. 2011-157536filed on Jul. 19, 2011. The entire disclosures of Japanese ApplicationNo. 2011-157536 is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resist composition and a method forproducing a resist pattern.

2. Background Information

A resist composition which contains a resin having a polymer containingstructural units represented by the formula (u-A) and the formula (u-B),and a polymer containing structural units represented by the formula(u-B), the formula (u-C) and the formula (u-D), as well as an acidgenerator, is described in Patent document of JP-2010-197413A.

However, a resist pattern formed with the conventional resistcomposition may be not always satisfied with because pattern collapsesand defects occur.

SUMMARY OF THE INVENTION

The present invention provides following inventions of <1> to <8>.

<1> A resist composition having

a resin having a structural unit represented by the formula (I),

a resin being insoluble or poorly soluble in alkali aqueous solution,but becoming soluble in an alkali aqueous solution by the action of anacid and not including the structural unit represented by the formula(I), and

an acid generator represented by the formula (II),

wherein R¹ represents a hydrogen atom or a methyl group;

A¹ represents a C₁ to C₆ alkanediyl group;

A¹³ represents a C₁ to C₁₈ divalent aliphatic hydrocarbon group thatoptionally has one or more halogen atoms;

X¹² represents *—CO—O— or *—O—CO—, * represents a bond to A¹³;

A¹⁴ represents a C₁ to C₁₇ aliphatic hydrocarbon group that optionallyhas one or more halogen atoms;

wherein R²³ and R²⁴ independently represent a fluorine atom or a C₁ toC₆ perfluoroalkyl group;

X²¹ represents an C₁ to C₁₇ divalent saturated hydrocarbon group, one ormore hydrogen atom contained in the divalent saturated hydrocarbon groupmay be replaced by a fluorine atom, and one or more —CH₂— contained inthe divalent saturated hydrocarbon group may be replaced by —O— or —CO—;

R²⁵ represents a group having cyclic ether structure; and

Z¹⁺ represents an organic cation.

<2> The resist composition according to <1>, wherein A¹ in the formula(I) is an ethylene group.

<3> The resist composition according to <1> or <2>, wherein A¹³ in theformula (I) is a C₁ to C₆ perfluoro alkanediyl group.

<4> The resist composition according to any one of <1> to <3>, whereinX¹² in the formula (I) is *—CO—O—, * represents a bond to A¹³.

<5> The resist composition according to any one of <1> to <4>, whereinA¹⁴ in the formula (I) is a cyclopropylmethyl, cyclopentyl, cyclohexyl,norbornyl or adamantyl group.

<6> The resist composition according to any one of <1> to <5>, whereinR²⁵ in the formula (II) is a group represented by the formula (IIA) orthe formula (IIE).

wherein s1 represents an integer of 1 to 4,

t1 represents an integer of 0 to 2,

provided that s1+t1 represents an integer of 1 to 4;

s11 represents an integer of 1 to 4,

t11 represents an integer of 0 to 2;

s12 represents an integer of 1 to 4,

t12 represents an integer of 0 to 2,

provided that s12+t12 represents an integer of 0 to 4;

R²⁶ in each occurrence represents a C₁ to C₁₂ saturated hydrocarbongroup, a C₆ to C₁₈ aromatic hydrocarbon group, or two R²⁶ are bondedtogether to form a ring, and one or more hydrogen atoms contained in thesaturated hydrocarbon group and the aromatic hydrocarbon group may bereplaced by a C₁ to C₆ alkyl group or a nitro group, and one or more—CH₂— contained in the saturated hydrocarbon group and ring may bereplaced by —O—;

u1 represents an integer of 0 to 8;

R²⁷ and R²⁸ in each occurrence independently represent a hydroxy group,a halogen atom, a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxyl group, a C₁to C₆ hydroxy alkyl group, a C₂ to C₇ acyl group, a C₂ to C₇ acyloxygroup or a C₂ to C₇ acylamino group, or two of R²⁷ and R²⁸ may be bondedtogether to form a single bond or a ring;

u2 and u3 independently represent an integer of 0 to 16;

* represent a bond to X²¹.

<7> The resist composition according to any one of <1> to <6>, whichfurther comprises a solvent.

<8> A method for producing a resist pattern comprising steps of;

(1) applying the resist composition any one of <1> to <7> onto asubstrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the chemical structure formulas of the present specification, unlessotherwise specified, the suitable choice of carbon number made for theexemplified substituent groups are applicable in all of the chemicalstructure formulas that have those same substituent groups. Unlessotherwise specified, these can include any of straight-chain, branchedchain, cyclic structure and a combination thereof. When there is astereoisomeric form, all stereoisomeric forms included.

“(Meth)acrylic monomer” means at least one monomer having a structure of“CH₂═CH—CO—” or “CH₂═C(CH₃)—CO—”, as well as “(meth)acrylate” and“(meth)acrylic acid” mean “at least one acrylate or methacrylate” and“at least one acrylic acid or methacrylic acid,” respectively.

<Resist Composition>

The resist composition of the present invention contains;

a resin (hereinafter is sometimes referred to as “resin (A)”), and

an acid generator represented by the formula (II) (hereinafter issometimes referred to as “acid generator (II)”).

Further, the present resist composition preferably contains a solvent(hereinafter is sometimes referred to as “solvent (E)”) and/or anadditive such as a basic compound (hereinafter is sometimes referred toas “basic compound (C)”) which is known as a quencher in this technicalfield, as needed.

<Resin (A)>

The resin (A) includes;

a resin having a structural unit represented by the formula (I)(hereinafter is sometimes referred to as “resin (A1)”), and

a resin being insoluble or poorly soluble in alkali aqueous solution,but becoming soluble in an alkali aqueous solution by the action of anacid and not including the structural unit represented by the formula(I) (hereinafter is sometimes referred to as “resin (A2)”).

Also, the resin (A) may contain a structural unit other than the resin(A1) and resin (A2).

<Resin (A)>

The resin (A) includes;

a resin having a structural unit represented by the formula (I)(hereinafter is sometimes referred to as “resin (A1)”), and

a resin being insoluble or poorly soluble in alkali aqueous solution,but becoming soluble in an alkali aqueous solution by the action of anacid and not including the structural unit represented by the formula(I) (hereinafter is sometimes referred to as “resin (A2)”).

Also, the resin (A) may contain a structural unit other than the resin(A1) and resin (A2).

<Resin (A1)>

The resin (A1) has a structural unit represented by the formula (I)(hereinafter is sometimes referred to as “structural unit (I)”).

wherein R¹ represents a hydrogen atom or a methyl group;

A¹ represents a C₁ to C₆ alkanediyl group;

A¹³ represents a C₁ to C₁₈ divalent aliphatic hydrocarbon group thatoptionally has one or more halogen atoms;

X¹² represents *—CO—O— or *—O—CO—;

* represents a bond to A¹³;

A¹⁴ represents a C₁ to C₁₇ aliphatic hydrocarbon group that optionallyhas one or more halogen atoms.

In the formula (I), examples of the alkanediyl group of A¹ include achain alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl; abranched alkanediyl group such as 1-methylpropane-1,3-diyl,2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl,1-methylbutane-1,4-diyl, 2-methylbutane-1,4-diyl groups.

Examples of the halogen atom of A¹³ include a fluorine, chlorine,bromine and iodine atoms. The fluorine atom is preferable.

The divalent aliphatic hydrocarbon group of A¹³ may be any of a chainand cyclic aliphatic hydrocarbon groups, and a combination of two ormore such groups. The aliphatic hydrocarbon group may include acarbon-carbon double bond, is preferably a saturated aliphatichydrocarbon group, and more preferably an alkanediyl group and adivalent alicyclic hydrocarbon group.

The aliphatic hydrocarbon group that optionally has one or more halogenatoms of A¹³ is preferably a saturated aliphatic hydrocarbon group thatoptionally has one or more fluorine atoms.

Examples of the chain divalent aliphatic hydrocarbon group thatoptionally has one or more halogen (preferably fluorine) atoms includemethylene, difluoromethylene, ethylene, perfluoroethylene, propanediyl,perfluoropropanediyl, butanediyl, perfluorobutanediyl, pentanediyl,perfluoropentanediyl, dichloromethylene and dibromomethylene groups.

The cyclic divalent aliphatic hydrocarbon group that optionally has oneor more halogen (preferably fluorine) atoms may be either monocyclic orpolycyclic hydrocarbon group. Examples thereof include a monocyclicaliphatic hydrocarbon group such as cyclohexanediyl,perfluorocyclohexanediyl and perchlorocyclohexanediyl; a polycyclicaliphatic hydrocarbon group such as adamantanediyl, norbornanediyl andperfluoro adamantanediyl groups.

The aliphatic hydrocarbon group of A¹⁴ may be any of a chain and cyclicaliphatic hydrocarbon groups, and a combination of two or more suchgroups. The aliphatic hydrocarbon group may include a carbon-carbondouble bond, is preferably a saturated aliphatic hydrocarbon group, andmore preferably an alkyl group and an alicyclic hydrocarbon group.

The aliphatic hydrocarbon group that optionally has one or more halogenatoms of A¹⁴ is preferably a saturated aliphatic hydrocarbon group thatoptionally has one or more fluorine atoms.

Examples of the chain aliphatic hydrocarbon group that optionally hasone or more halogen (preferably fluorine) atoms include difluoromethyl,trifluoromethyl, methyl, 1,1,1-trifluoroethyl, 1,1,2,2-tetrafluoroethyl,ethyl, perfluoroethyl, perfluoropropyl, 1,1,1,2,2-pentafluoropropyl,propyl, perfluorobutyl, 1,1,2,2,3,3,4,4-octafluorobutyl, butyl,perfluoropentyl, 1,1,1,2,2,3,3,4,4-nonafluoropentyl, pentyl, hexyl,perfluorohexyl, heptyl, perfluoroheptyl, octyl, perfluorooctyl,trichloromethyl, and tribromomethyl groups.

The cyclic aliphatic hydrocarbon group that optionally has one or morehalogen (preferably fluorine) atoms may be either monocyclic orpolycyclic hydrocarbon group. Examples thereof include the monocyclicaliphatic hydrocarbon group such as cyclopentyl, cyclohexyl,perfluorocyclohexyl and perchlorocyclohexyl; polycyclic aliphatichydrocarbon group such as adamantyl, norbornyl and perfluoro adamantylgroups.

Examples of the combination of the chain and cyclic aliphatichydrocarbon groups include cyclopropylmethyl, cyclopentylmethyl,cyclohexylmethyl, adamantylmethyl and perfluoro adamantylmethyl groups.

A¹ in the formula (I) is preferably a C₂ to C₄ alkanediyl group, andmore preferably an ethylene group.

The aliphatic hydrocarbon group of A¹³ is preferably a C₁ to C₆aliphatic hydrocarbon group, and more preferably a C₂ to C₃ aliphatichydrocarbon group.

The aliphatic hydrocarbon group of A¹⁴ is preferably a C₃ to C₁₂aliphatic hydrocarbon group, and more preferably a C₃ to C₁₀ aliphatichydrocarbon group. Among these, A¹⁴ is preferably a C₃ to C₁₂ aliphatichydrocarbon group which include an alicyclic hydrocarbon group, andstill more preferably cyclopropylmethyl, cyclopentyl, cyclohexyl,norbornyl and adamantyl groups.

Specific examples of the structural units (I) include as follows.

Also, examples of the structural units (I) include structural units inwhich a methyl group corresponding to R¹ in the structural unitsrepresented by the above is replaced by a hydrogen atom.

The structural unit (I) is derived from a compound represented by theformula (I′), hereinafter is sometimes referred to as “compound (I′)”.

wherein R¹, A¹, A¹³, X¹² and A¹⁴ have the same definition of the above.

The compound (I′) can be produced by a method below.

wherein R¹, A¹, A¹³, X¹² and A¹⁴ have the same definition of the above.

The compound (I′) can be obtained by reacting a compound represented bythe formula (Is-1) with a carboxylic acid represented by the formula(Is-2). This reaction is usually performed in presence of a solvent.Preferred examples of the solvent include tetrahydrofuran and toluene.This reaction may be coexistent with a known esterification catalyst,for example, an acid catalyst, carbodiimide catalyst.

As the compound represented by the formula (Is-1), a marketed product ora compound which is produced by a known method may be used. The knownmethod includes a method condensing (meth)acrylic acid or derivativesthereof, for example, (meth)acrylic chloride, with a suitable diol(HO-A¹-OH). The hydroxyethyl methacrylate can be used as a marketedproduct.

The carboxylic acid represented by the formula (Is-2) can be produced bya known method. Examples of the carboxylic acid represented by theformula (Is-2) include compounds below.

The resin (A1) may include a structural unit other than the structuralunit (I).

Examples of the structural unit other than the structural unit (I)include a structural unit derived from a monomer having an acid labilegroup described below (hereinafter is sometimes referred to as “acidlabile monomer (a1)”), a structural unit derived from a monomer nothaving an acid labile group described below (hereinafter is sometimesreferred to as “acid stable monomer”), a structural unit represented bythe formula (III-1) (hereinafter is sometimes referred to as “structuralunit (III-1)”) described below, a structural unit represented by theformula (III-2) (hereinafter is sometimes referred to as “structuralunit (III-2)”) described below, a structural unit derived from a knownmonomer in this field. Among these, the structural unit (III-1) and thestructural unit (III-2) are preferable.

wherein R¹¹ represents a hydrogen atom or a methyl group;

A¹¹ represents a C₁ to C₆ alkanediyl group;

R¹² represents a C₁ to C₁₀ hydrocarbon group having a fluorine atom.

wherein R²¹ represents a hydrogen atom or a methyl group;

ring W² represents a C₆ to C₁₀ hydrocarbon ring;

A²² represents —O—, *—CO—O— or * —O—CO—, * represents a bond to ring W²;

R²² represents a C₁ to C₆ alkyl group having a fluorine atom.

In the formula (III-1), examples of the alkanediyl group of A¹¹ includea chain alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl; abranched alkanediyl group such as 1-methylpropane-1,3-diyl,2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl,1-methylbutane-1,4-diyl and 2-methylbutane-1,4-diyl groups.

The hydrocarbon group having a fluorine atom of R¹² may be an alkylgroup having a fluorine atom and an alicyclic hydrocarbon group having afluorine atom.

Examples of the alkyl group include methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, tert-butyl, iso-butyl, n-pentyl, iso-pentyl,tert-pentyl, neo-pentyl and hexyl groups.

Examples of the alkyl group having a fluorine atom include a fluorinatedalkyl group such as, groups described below, difluoromethyl,trifluoromethyl, 1,1-difluoroethyl, 2,2-difluoroethyl,2,2,2-trifluoroethyl, perfluoroethyl, 1,1,2,2-tetrafluoropropyl,1,1,2,2,3,3-hexafluoropropyl, perfluoroethylmethyl,1-(trifluoromethyl)-1,2,2,2-tetrafluoroethyl, perfluoropropyl,1,1,2,2-tetrafluorobutyl, 1,1,2,2,3,3-hexafluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, perfluorobutyl,1,1-bis(trifluoro)methyl-2,2,2-trifluoroethyl, 2-(perfluoropropyl)ethyl,1,1,2,2,3,3,4,4-octafluoropentyl, perfluoropentyl,1,1,2,2,3,3,4,4,5,5-decafluoropentyl,1,1-bis(trifluoromethyl)-2,2,3,3,3-pentafluoropropyl, perfluoropentyl,2-(perfluorobutyl)ethyl, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl,1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyl, perfluoropentylmethyl andperfluorohexyl groups.

The alicyclic hydrocarbon group is preferably a saturated ring of analiphatic hydrocarbon group in which a hydrogen atom is removed.Examples of the saturated ring of an aliphatic hydrocarbon group includegroups below.

Examples of the alicyclic hydrocarbon group having a fluorine atominclude a fluorinated cycloalkyl group such as perfluorocyclohexyl andperfluoroadamantyl groups.

The hydrocarbon ring of ring W² may be an alicyclic hydrocarbon ring,and preferably a saturated alicyclic hydrocarbon ring. Examples of thesaturated alicyclic hydrocarbon ring include adamantane and cyclohexanerings, and adamantane ring is preferable.

Examples of the structural unit (III-1) include structural units below.

Also, examples of the structural units (III-1) include structural unitsin which a methyl group corresponding to R¹¹ in the structural unitsrepresented by the above is replaced by a hydrogen atom.

Examples of the structural unit (III-2) include structural units below.

Also, examples of the structural units (III-2) include structural unitsin which a methyl group corresponding to R²¹ in the structural unitsrepresented by the above is replaced by a hydrogen atom.

The proportion of the structural unit (I) in the resin (A1) is generally5 to 100 mol %, preferably 10 to 100 mol %, with respect to the totalstructural units (100 mol %) constituting the resin (A1).

When the resin (A1) contains the structural unit (III-1) and/or thestructural unit (III-2), the total proportion thereof in the resin (A1)is generally 1 to 95 mol %, preferably 2 to 80 mol %, more preferably 5to 70 mol %, still more preferably 5 to 50 mol % and in particularpreferably 5 to 30 mol %, with respect to the total structural units(100 mol %) constituting the resin (A1).

The weight ratio of the structural unit (III-1): the structural unit(III-2) is preferably, for example, 0:100 to 100:0, more preferably 3:97to 97:3, still more preferably 50:50 to 95:5.

For achieving the proportion of the structural unit (I), the structuralunit (III-1) and/or the structural unit (III-2) in the resin (A1) withinthe above range, the amount of the compound (I′), a monomer giving thestructural unit (III-1) and/or a monomer giving the structural unit(III-2) to be used can be adjusted with respect to the total amount ofthe monomer to be used when the resin (A1) is produced (the same shallapply hereinafter for corresponding adjustment of the proportion).

The resin (A1) can be produced by a known polymerization method, forexample, radical polymerization method, using at least one of thecompound (I′), at least one monomer giving the structural unit (III-1)and/or at least one of the monomer giving the structural unit (III-2),as well as optionally at least one of the acid labile monomer (a1), atleast one of the acid stable monomer and/or at least one of a knowncompound, described below.

The weight average molecular weight of the resin (A1) is preferably5,000 or more (more preferably 7,000 or more, and still more preferably10,000 or more), and 80,000 or less (more preferably 50,000 or less, andstill more preferably 30,000 or less).

The weight average molecular weight is a value determined by gelpermeation chromatography using polystyrene as the standard product. Thedetailed condition of this analysis is described in Examples.

<Resin (A2)>

The resin (A2) is a resin having properties which is insoluble or poorlysoluble in alkali aqueous solution, but becomes soluble in an alkaliaqueous solution by the action of an acid. Here “a resin becomingsoluble in an alkali aqueous solution by the action of an acid” means aresin that has an acid labile group and is insoluble or poorly solublein aqueous alkali solution before contact with the acid, and becomessoluble in aqueous alkali solution after contact with an acid.

Therefore, the resin (A2) is preferably a resin having at least onestructural unit derived from an acid labile monomer (a1).

Also, the resin (A2) may include a structural unit other than thestructural unit having the acid labile group as long as the resin (A2)has above properties and does not have the structural unit (I).

Examples of the structural unit other than the structural unit havingthe acid labile group include a structural unit derived from the acidstable monomer, the structural unit derived from a known monomer in thisfield, structural unit (III-1) and/or the structural unit (III-2)described above.

<Acid Labile Monomer (a1)>

The “acid labile group” means a group which has an elimination group andin which the elimination group is detached by contacting with an acidresulting in forming a hydrophilic group such as a hydroxy or carboxygroup. Examples of the acid labile group include a group represented bythe formula (1) and a group represented by the formula (2). Hereinaftera group represented by the formula (1) sometimes refers to as an “acidlabile group (1)”, and a group represented by the formula (2) sometimesrefers to as an “acid labile group (2)”.

wherein R^(a1) to R^(a3) independently represent a C₁ to C₈ alkyl groupor a C₃ to C₂₀ alicyclic hydrocarbon group, or R^(a1) and R^(a2) may bebonded together to form a C₂ to C₂₀ divalent hydrocarbon group, *represents a bond. In particular, the bond here represents a bondingsite (the similar shall apply hereinafter for “bond”).

wherein R^(a1′) and R^(a2′) independently represent a hydrogen atom or aC₁ to C₁₂ hydrocarbon group, R^(a3′) represents a C₁ to C₂₀ hydrocarbongroup, or R^(a2′) and R^(a3′) may be bonded together to form a divalentC₂ to C₂₀ hydrocarbon group, and one or more —CH₂-contained in thehydrocarbon group or the divalent hydrocarbon group may be replaced by—O— or —S—, * represents a bond.

Examples of the alkyl group of R^(a1) to R^(a3) include methyl, ethyl,propyl, butyl, pentyl and hexyl groups.

Examples of the alicyclic hydrocarbon group of R^(a1) to R^(a3) includemonocyclic hydrocarbon groups such as a cycloalkyl group, i.e.,cyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl,cycloheptyl, cyclooctyl groups; and polycyclic hydrocarbon groups suchas decahydronaphtyl, adamantyl, norbornyl (i.e., bicyclo[2.2.1]heptyl),and methyl norbornyl groups as well as groups below.

The hydrogen atom contained in the alicyclic hydrocarbon group of R^(a1)to R^(a3) may be replaced an alkyl group. In this case, the carbonnumber of the alicyclic hydrocarbon group is comparable to the totalcarbon number of the alkyl group and the alicyclic hydrocarbon group.

The alicyclic hydrocarbon group of R^(a1) to R^(a3) preferably has 3 to16 carbon atoms, and more preferably has 4 to 16 carbon atoms.

When R^(a1) and R^(a2) is bonded together to form a C₂ to C₂₀ divalenthydrocarbon group, examples of the group-C(R^(a1))(R^(a2))(R^(a3))include groups below. The divalent hydrocarbon group preferably has 3 to12 carbon atoms. * represents a bond to —O—.

Specific examples of the acid labile group (1) include, for example,

1,1-dialkylalkoxycarbonyl group (a group in which R^(a1) to R^(a3) arealkyl groups, preferably tert-butoxycarbonyl group, in the formula (1)),

2-alkyladamantane-2-yloxycarbonyl group (a group in which R^(a1), R^(a2)and a carbon atom form adamantyl group, and R^(a3) is alkyl group, inthe formula (1)), and

1-(adamantane-1-yl)-1-alkylalkoxycarbonyl group (a group in which R^(a1)and R^(a2) are alkyl group, and R^(a3) is adamantyl group, in theformula (1)).

The hydrocarbon group of R^(a1′) to R^(a3′) includes any of an alkylgroup, an alicyclic hydrocarbon group and an aromatic hydrocarbon group.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl,p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the divalent hydrocarbon group which is formed by bondingwith R^(a2′) and R^(a3′) include a a divalent aliphatic hydrocarbongroup.

At least one of R^(a1′) and R^(a2′) is preferably a hydrogen atom.

Specific examples of the acid labile group (2) include a group below.

The acid labile monomer (a1) is preferably a monomer having an acidlabile group and a carbon-carbon double bond, and more preferably a(meth)acrylic monomer having the acid labile group.

Among the (meth)acrylic monomer having an acid labile group, it ispreferably a monomer having a C₅ to C₂₀ alicyclic hydrocarbon group.When a resin which can be obtained by polymerizing monomers having bulkystructure such as the alicyclic hydrocarbon group is used, the resistcomposition having excellent resolution tends to be obtained during theproduction of a resist pattern.

Examples of the (meth)acrylic monomer having the acid labile group (1)and a carbon-carbon double bond preferably include a monomer representedby the formula (a1-1) and a monomer represented by the formula (a1-2),below (hereinafter are sometimes referred to as a “monomer (a1-1)” and a“monomer (a1-2)”). These may be used as a single monomer or as acombination of two or more monomers.

wherein L^(a1) and L^(a2) independently represent *—O— or*—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, * represents abond to the carbonyl group;

R^(a4) and R^(a5) independently represent a hydrogen atom or a methylgroup;

R^(a6) and R^(a7) independently represent a C₁ to C₈ alkyl group or a C₃to C₁₀ alicyclic hydrocarbon group;

m1 represents an integer 0 to 14;

n1 represents an integer 0 to 10; and

n1′ represents an integer 0 to 3.

In the formula (a1-1) and the formula (a1-2), L^(a1) and L^(a2) arepreferably *—O— or *—O—(CH₂)_(k1′)—CO—O—, here k1′ represents an integerof 1 to 4 and more preferably 1, and more preferably *—O.

R^(a4) and R^(a5) are preferably a methyl group.

Examples of the alkyl group of R^(a6) and R^(a7) include methyl, ethyl,propyl, butyl, pentyl, hexyl and octyl groups. Among these, the alkylgroup of R^(a6) and R^(a7) is preferably a C₁ to C₆ alkyl group.

Examples of the alicyclic hydrocarbon group of R^(a6) and R^(a7) includemonocyclic hydrocarbon groups such as cyclopentyl, cyclohexyl,methylcyclohexyl, dimethylcyclohexyl, cycloheptyl, cyclooctyl groups;and polycyclic hydrocarbon groups such as decahydronaphtyl, adamantyl,norbornyl (i.e., bicyclo[2.2.1]heptyl), and methyl norbornyl groups aswell as groups above. Among these, the alicyclic hydrocarbon group ofR^(a6) and R^(a7) is preferably a C₃ to C₈ alicyclic hydrocarbon group,and more preferably a C₃ to C₆ alicyclic hydrocarbon group.

m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1′ is preferably 0 or 1, and more preferably 1.

Examples of the monomer (a1-1) include monomers described in JP2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a1-1-1) to the formula (a1-1-8), and morepreferably monomers represented by the formula (a1-1-1) to the formula(a1-1-4) below.

Examples of the monomer (a1-2) include1-ethyl-1-cyclopentane-1-yl(meth)acrylate,1-ethyl-1-cyclohexane-1-yl(meth)acrylate,1-ethyl-1-cycloheptane-1-yl(meth)acrylate,1-methyl-1-cyclopentane-1-yl(meth)acrylate and1-isopropyl-1-cyclopentane-1-yl(meth)acrylate. Among these, the monomersare preferably monomers represented by the formula (a1-2-1) to theformula (a1-2-12), and more preferably monomers represented by theformula (a1-2-3), the formula (a1-2-4), the formula (a1-2-9) and theformula (a1-2-10), and still more preferably monomers represented by theformula (a1-2-3) and the formula (a1-2-9) below.

When the resin (A2) contains the structural unit (a1-1) and/or thestructural unit (a1-2), the total proportion thereof is generally 10 to95 mol %, preferably 15 to 90 mol %, more preferably 20 to 85 mol %,with respect to the total structural units (100 mol %) of the resin(A2).

Examples of a monomer having an acid-labile group (2) and acarbon-carbon double bond include a monomer represented by the formula(a1-5). Such monomer is sometimes hereinafter referred to as “monomer(a1-5)”. When the resin (A2) has the structural unit derived from themonomer (a1-5), a resist pattern tends to be obtained with less defects.

wherein R³¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆alkyl group that optionally has a halogen atom;

Z¹ represents a single bond or *—O—(CH₂)_(k4)—CO-L⁴-, k4 represents aninteger of 1 to 4, * represents a bond to L¹;

L¹, L², L³ and L⁴ independently represent *—O— or *—S—.

s1 represents an integer of 1 to 3;

s1′ represents an integer of 0 to 3.

In the formula (a1-5), R³¹ is preferably a hydrogen atom, a methyl groupor trifluoromethyl group;

L¹ is preferably —O—;

L² and L³ are independently preferably *—O— or *—S—, and more preferably—O— for one and —S— for another;

s1 is preferably 1;

s1′ is preferably an integer of 0 to 2;

Z¹ is preferably a single bond or —CH₂—CO—O—.

Examples of the monomer (a1-5) include monomers below.

When the resin (A2) contains the structural unit derived from themonomer (a1-5), the proportion thereof is generally 1 to 50 mol %,preferably 3 to 45 mol %, and more preferably 5 to 40 mol %, withrespect to the total structural units (100 mol %) constituting the resin(A2).

<Acid Stable Monomer>

As the acid stable monomer, a monomer having a hydroxy group or alactone ring is preferable. When a resin containing the structural unitderived from a monomer having hydroxy group (hereinafter such acidstable monomer is sometimes referred to as “acid stable monomer (a2)”)or a acid stable monomer having a lactone ring (hereinafter such acidstable monomer is sometimes referred to as “acid stable monomer (a3)”)is used, the adhesiveness of resist pattern to a substrate andresolution of resist pattern tend to be improved.

<Acid Stable Monomer (a2)>

The acid stable monomer (a2), which has a hydroxy group, is preferablyselected depending on the kinds of an exposure light source at producingthe resist pattern.

When KrF excimer laser lithography (248 nm), or high-energy irradiationsuch as electron beam or EUV light is used for the resist composition,using the acid stable monomer having a phenolic hydroxy group such ashydroxystyrene as the acid stable monomer (a2) is preferable.

When ArF excimer laser lithography (193 nm), i.e., short wavelengthexcimer laser lithography is used, using the acid stable monomer havinga hydroxy adamantyl group represented by the formula (a2-1) as the acidstable monomer (a2) is preferable.

The acid stable monomer (a2) having the hydroxy group may be used as asingle monomer or as a combination of two or more monomers.

Examples of the acid stable monomer having hydroxy adamantyl include themonomer represented by the formula (a2-1).

wherein La³ represents —O— or *—O—(CH₂)_(k2)—CO—O—;

k2 represents an integer of 1 to 7;

* represents a bind to —CO—;

R^(a14) represents a hydrogen atom or a methyl group;

R^(a15) and R^(a16) independently represent a hydrogen atom, a methylgroup or a hydroxy group;

o1 represents an integer of 0 to 10.

In the formula (a2-1), L^(a3) is preferably —O—, —O—(CH₂)_(f1)—CO—O—,here f1 represents an integer of 1 to 4, and more preferably —O—.

R^(a14) is preferably a methyl group.

R^(a15) is preferably a hydrogen atom.

R^(a16) is preferably a hydrogen atom or a hydroxy group.

o1 is preferably an integer of 0 to 3, and more preferably an integer of0 or 1.

Examples of the acid stable monomer (a2-1) include monomers described inJP 2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a2-1-1) to the formula (a2-1-6), morepreferably monomers represented by the formula (a2-1-1) to the formula(a2-1-4), and still more preferably monomers represented by the formula(a2-1-1) and the formula (a2-1-3) below.

When the resin (A2) contains the acid stable structural unit derivedfrom the monomer represented by the formula (a2-1), the proportionthereof is generally 3 to 45 mol %, preferably 5 to 40 mol %, morepreferably 5 to 35 mol %, and still more preferably 5 to 30 mol %, withrespect to the total structural units (100 mol %) constituting the resin(A2).

<Acid Stable Monomer (a3)>

The lactone ring included in the acid stable monomer (a3) may be amonocyclic compound such as β-propiolactone ring, γ-butyrolactone,δ-valerolactone, or a condensed ring with monocyclic lactone ring andother ring. Among these, γ-butyrolactone and condensed ring withγ-butyrolactone and other ring are preferable.

Examples of the acid stable monomer (a3) having the lactone ring includemonomers represented by the formula (a3-1), the formula (a3-2) and theformula (a3-3). These monomers may be used as a single monomer or as acombination of two or more monomers.

wherein L^(a4) to L^(a6) independently represent —O— or*—O—(CH₂)_(k3)—CO—O—;

k3 represents an integer of 1 to 7, * represents a bind to —CO—;

R^(a18) to R^(a20) independently represent a hydrogen atom or a methylgroup;

R^(a21) in each occurrence represents a C₁ to C₄ alkyl group;

p1 represents an integer of 0 to 5;

R^(a22) to R^(a23) in each occurrence independently represent a carboxylgroup, cyano group, and a C₁ to C₄ alkyl group;

q1 and r1 independently represent an integer of 0 to 3.

In the formulae (a3-1) to (a3-3), L^(a4) to L^(a6) include the samegroup as described in L^(a3) above, and are independently preferably—O—, *—O—(CH₂)_(k3′)—CO—O—, here k3′ represents an integer of 1 to 4(preferably 1), and more preferably —O—;

R^(a18) to R^(a21) are independently preferably a methyl group.

R^(a22) and R^(a23) are independently preferably a carboxyl group, cyanogroup or methyl group;

p1 to r1 are independently preferably an integer of 0 to 2, and morepreferably an integer of 0 or 1.

Examples of the monomer (a3) include monomers described in JP2010-204646A. Among these, the monomers are preferably monomersrepresented by the formula (a3-1-1) to the formula (a3-1-4), the formula(a3-2-1) to the formula (a3-2-4), the formula (a3-3-1) to the formula(a3-3-4), more preferably monomers represented by the formula (a3-1-1)to the formula (a3-1-2), the formula (a3-2-3) to the formula (a3-2-4),and still more preferably monomers represented by the formula (a3-1-1)and the formula (a3-2-3) below.

When the resin (A2) contains the structural units derived from the acidstable monomer (a3) having the lactone ring, the total proportionthereof is preferably 5 to 70 mol %, more preferably 10 to 65 mol %,still more preferably 15 to 60 mol %, with respect to the totalstructural units (100 mol %) constituting the resin (A2).

When the resin (A2) is the copolymer of the acid labile monomer (a1) andthe acid stable monomer, the proportion of the structural unit derivedfrom the acid labile monomer (a1) is preferably 10 to 80 mol %, and morepreferably 20 to 60 mol %, with respect to the total structural units(100 mol %) constituting the resin (A2).

The resin (A2) preferably contains 15 mol % or more of the structuralunit derived from the monomer having an adamantyl group (in particular,the monomer having the acid labile group (a1-1)) with respect to thestructural units derived from the acid labile monomer (a1). As the moleratio of the structural unit derived from the monomer having anadamantyl group increases within this range, the dry etching resistanceof the resulting resist improves.

The resin (A2) preferably is a copolymer of the acid labile monomer (a1)and the acid stable monomer. In this copolymer, the acid labile monomer(a1) is preferably at least one of the acid labile monomer (a1-1) havingan adamantyl group and the acid labile monomer (a1-2) having acyclohexyl group, and more preferably is the acid labile monomer (a1-1).

The acid stable monomer is preferably the acid stable monomer (a2)having a hydroxy group and/or the acid stable monomer (a3) having alactone ring. The acid stable monomer (a2) is preferably the monomerhaving the hydroxyadamantyl group (a2-1). The acid stable monomer (a3)is preferably at least one of the monomer having the γ-butyrolactonering (a3-1) and the monomer having the condensed ring of theγ-butyrolactone ring and the norbornene ring (a3-2).

The resin (A2) can be produced by a known polymerization method, forexample, radical polymerization method, using at least one of the acidlabile monomer (a1) and/or at least one of the acid stable monomer (a2)having a hydroxy group and/or at least one of the acid stable monomer(a3) having a lactone ring and/or at least one of a known compound.

The weight average molecular weight of the resin (A2) is preferably2,500 or more (more preferably 3,000 or more, and still more preferably4,000 or more), and 50,000 or less (more preferably 30,000 or less, andstill more preferably 10,000 or less).

In the present resist composition, the weight ratio of the resins(A1)/(A2) is preferably, for example, 0.01/10 to 5/10, more preferably0.05/10 to 3/10, still more preferably 0.1/10 to 2/10, in particular,preferably 0.2/10 to 1/10.

<Resin Other than Resin (A1) and Resin (A2)>

The resist composition of the present invention may include a resinother than the resin (A1) and the resin (A2) described above. Such resinis a resin having at least one of the structural unit derived from theacid labile monomer (a1), at least one of the structural unit derivedfrom the acid stable monomer, as described above, and/or at least one ofthe structural unit derived from a known monomer in this field.

The proportion of the resin (A) can be adjusted with respect to thetotal solid proportion of the resist composition. For example, theresist composition of the present invention preferably contains 80weight % or more and 99 weight % or less of the resin (A), with respectto the total solid proportion of the resist composition.

In the specification, the term “solid proportion of the resistcomposition” means the entire proportion of all ingredients other thanthe solvent (E).

The proportion of the resin (A) and the solid proportion of the resistcomposition can be measured with a known analytical method such as, forexample, liquid chromatography and gas chromatography.

<Acid generator (II)>

The acid generator (II) included in the resist composition of thepresent invention is represented by the formula (II);

wherein R²³ and R²⁴ independently represent a fluorine atom or a C₁ toC₆ perfluoroalkyl group;

X²¹ represents an C₁ to C₁₇ divalent saturated hydrocarbon group, one ormore hydrogen atom contained in the divalent saturated hydrocarbon groupmay be replaced by a fluorine atom, and one or more —CH₂— contained inthe divalent saturated hydrocarbon group may be replaced by —O— or —CO—;

R²⁵ represents a group having cyclic ether structure; and

Z¹⁺ represents an organic cation.

In the formula (II), a moiety having a negative charge in which anorganic cation, Z¹⁺, having a positive charge is removed sometimesrefers to as a sulfonate anion.

Examples of the perfluoroalkyl group of R²³ and R²⁴ includetrifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl,perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl,perfluoropentyl and perfluorohexyl groups.

Among these, R²³ and R²⁴ independently are preferably trifluoromethyl orfluorine atom, and more preferably a fluorine atom.

Examples of the a divalent saturated hydrocarbon group of X²¹ includeany of;

a chain alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl,heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl,undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl,tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl,heptadecane-1,17-diyl, ethane-1,1-diyl, propan-1,1-diyl andpropan-2,2-diyl groups;

a branched chain alkanediyl group such as a group in which a chainalkanediyl group is bonded a side chain of a C₁ to C₄ alkyl group suchas methyl, ethyl, propyl, isopropyl, butyl, sec-butyl and tert-butyl,for example, butane-1,3-diyl, 2-methylpropane-1,3-diyl,2-methylpropane-1,2-diyl, pentane-1,4-diyl and 2-methylbutane-1,4-diylgroups;

a mono-alicyclic saturated hydrocarbon group such as a cycloalkanediylgroup (e.g., cyclobutan-1,3-diyl, cyclopentan-1,3-diyl,cyclohexane-1,4-diyl and cyclooctan-1,5-diyl groups);

a poly-alicyclic saturated hydrocarbon group such asnorbornane-2,3-diyl, norbornane-1,4-diyl, norbornane-2,5-diyl,adamantane-1,5-diyl and adamantane-2,6-diyl groups; and

a combination of two or more groups.

Examples of the saturated hydrocarbon group of X²¹ in which one or more—CH₂— contained in the saturated hydrocarbon group is replaced by —O— or—CO— include groups represented by the formula (b1-1) to the formula(b1-6) below. In the formula (b1-1) to the formula (b1-6), the group isrepresented so as to correspond with two sides of the formula (II), thatis, the left side of the group bonds to C(R²³)(R²⁴)—) and the right sideof the group bonds to —R²⁵ (examples of the formula (b1-1) to theformula (b1-6) are the same as above). * represents a bond.

wherein L^(b2) represents a single bond or a C₁ to C₁₅ divalentsaturated hydrocarbon group;

L^(b3) represents a single bond or a C₁ to C₁₂ divalent saturatedhydrocarbon group;

L^(b4) represents a C₁ to C₁₃ divalent saturated hydrocarbon group, thetotal number of the carbon atoms in L^(b3) and L^(b4) is at most 13;

L^(b5) represents a C₁ to C₁₅ divalent saturated hydrocarbon group;

L^(b6) and L^(b7) independently represent a C₁ to C₁₅ divalent saturatedhydrocarbon group, the total number of the carbon atoms in L^(b6) andL^(b7) is at most 16;

L^(b8) represents a C₁ to C₁₄ divalent saturated hydrocarbon group;

L^(b9) and L^(b10) independently represent a C₁ to C₁₁ divalentsaturated hydrocarbon group, the total number of the carbon atoms inL^(b9) and L^(b10) is at most 12.

Among these, X²¹ is preferably the groups represented by the formula(b1-1) to the formula (b1-4), more preferably the group represented bythe formula (b1-1) or the formula (b1-2), and still more preferably thegroup represented by the formula (b1-1). In particular, the divalentgroup represented by the formula (b1-1) in which L^(b2) represents asingle bond or —CH₂— is preferable.

Specific examples of the divalent group represented by the formula(b1-1) include groups below. In the formula below, * represent a bond.

Specific examples of the divalent group represented by the formula(b1-2) include groups below.

Specific examples of the divalent group represented by the formula(b1-3) include groups below.

Specific examples of the divalent group represented by the formula(b1-4) include a group below.

Specific examples of the divalent group represented by the formula(b1-5) include groups below.

Specific examples of the divalent group represented by the formula(b1-6) include groups below.

The group having cyclic ether structure of R²⁵ may be either monocyclicether structure or polycyclic ether structure. Also, the group havingcyclic ether structure includes one or more substituents. The ringstructure having an oxygen atom in the monocyclic ether structure orpolycyclic ether structure preferably has two to five carbon atoms.

Examples of the group having cyclic ether structure include a grouprepresented by the formula (IIA) and a group represented by the formula(IIE).

wherein s1 represents an integer of 1 to 4,

t1 represents an integer of 0 to 2,

provided that s1+t1 represents an integer of 1 to 4;

s11 represents an integer of 1 to 4,

t11 represents an integer of 0 to 2;

s12 represents an integer of 1 to 4,

t12 represents an integer of 0 to 2,

provided that s12+t12 represents an integer of 0 to 4;

R²⁶ in each occurrence represents a C₁ to C₁₂ saturated hydrocarbongroup, a C₆ to C₁₈ aromatic hydrocarbon group, or two R²⁶ are bondedtogether to form a ring, and one or more hydrogen atoms contained in thesaturated hydrocarbon group and the aromatic hydrocarbon group may bereplaced by a C₁ to C₆ alkyl group or a nitro group, and one or more—CH₂— contained in the saturated hydrocarbon group and ring may bereplaced by —O—;

u1 represents an integer of 0 to 8;

R²⁷ and R²⁸ in each occurrence independently represent a hydroxy group,a halogen atom, a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxyl group, a C₁to C₆ hydroxy alkyl group, a C₂ to C₇ acyl group, a C₂ to C₇ acyloxygroup or a C₂ to C₇ acylamino group, or two of R²⁷ and R²⁸ may be bondedtogether to form a single bond or a ring;

u2 and u3 independently represent an integer of 0 to 16;

-   -   * represent a bond to X²¹.

Examples of the saturated hydrocarbon group of R²⁶ include an alkylgroup, a cyclic hydrocarbon groups (including a spiro ring group).

Examples of the alkyl group include methyl, ethyl, propyl, butyl,pentyl, hexyl, heptyl and octyl groups.

Examples of the cyclic hydrocarbon group include monocyclic hydrocarbongroups such as a cycloalkyl group, i.e., cyclopentyl, cyclohexyl,methylcyclohexyl, dimethylcyclohexyl, cycloheptyl, cyclooctyl groups;and polycyclic hydrocarbon groups such as decahydronaphtyl, adamantyl,norbornyl and methyl norbornyl groups as well as groups below.

Among these, a cycloalkyl, cyclohexyl and adamantyl groups arepreferable as the saturated hydrocarbon.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl,p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

When two R⁶ are bonded together to form a ring, the ring may be any of asaturated or an unsaturated ring. Two R⁶ bonded together to form a ringmay bond to different carbon atoms or the same carbon atom,respectively.

Examples of the halogen atom of R²⁷ and R²⁸ include fluorine, chlorine,bromine and iodine atoms.

Examples of the alkyl group are the same examples as described above.

Examples of the alkoxyl group include methoxy, ethoxy, n-propoxy,isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentyloxy andn-hexyloxy groups.

Examples of the hydroxyalkyl group include hydroxymethyl andhydroxyethyl groups

Examples of the acyl group include acetyl, propionyl and butyryl groups.

Examples of the acyloxy group include acetyloxy, propionyloxy andbutyryloxy groups.

Examples of the acylamino group include acetylamino, propionylamino andbutyrylamino groups.

When two of R²⁷ and R²⁸ are bonded together to form a single bond, twoR²⁸ preferably are bonded together to form a single bond.

s1 is preferably 1, t1 is preferably 0 or 1, and s1+t1 is preferably 1or 2.

s12+t12 is preferably 1 or 2.

Examples of the group represented by the formula (IIA) include groupsbelow.

Examples of the group represented by the formula (IIE) include groupsbelow.

Specific examples of the group represented by the formula (IIA) includegroups below.

Specific examples of the group represented by the formula (IIE) includegroups below.

As the group having cyclic ether structure of R²⁵, a group including aC₂ to C₅ cyclic ether structure is preferable. Example thereof includegroups containing an oxirane ring, oxetane ring, 5-membered cyclic etherstructure having four carbon atoms and 6-membered cyclic ether structurehaving five carbon atoms.

Among these, ether ring structures such as 3-membered ether ring havingtwo carbon atoms (i.e., oxirane ring) and 4-membered cyclic etherstructure having three carbon atoms (i.e., oxetane ring) are preferable,ether ring structures of 3-membered cyclic ether structure having twocarbon atoms (i.e., oxirane ring) is more preferable.

The acid generator (II) is preferably an acid generator represented bythe formula (II-a) or the formula (II-b). The acid generator representedby the formula (II-a) is preferable.

wherein s1, t1, s11, t11, s12, t12, R²³, R²⁴, R²⁶, R²⁷, R²⁸, X²¹, u1,u2, u3 and Z¹⁺ have the same definition of the above.

Examples of the acid generator (II) include salts below.

Examples of the cation Z¹⁺ of the acid generator (II) include an organiconium cation such as an organic sulfonium cation, organic iodoniumcation, organic ammonium cation, organic benzothiazolium cation andorganic phosphonium cation. Among these, organic sulfonium cation andorganic iodonium cation are preferable, and aryl sulfonium cation ismore preferable.

Z¹⁺ of the formula (II) is preferably represented by any of the formula(b2-1) to the formula (b2-4).

wherein R^(b4), R^(b5) and R^(b6) independently represent a C₁ to C₃₀alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group or a C₆ to C₃₆aromatic hydrocarbon group, or R^(b4) and R^(b5) may be bonded togetherto form a sulfur-containing ring, one or more hydrogen atoms containedin the alkyl group may be replaced by a hydroxy group, a C₃ to C₁₈alicyclic hydrocarbon group, a C₁ to C₁₂ alkoxy group or a C₆ to C₁₈aromatic hydrocarbon group, one or more hydrogen atoms contained in thealicyclic hydrocarbon group may be replaced by a halogen atom, a C₁ toC₁₈ alkyl group, a C₂ to C₄ acyl group and a glycidyloxy group, one ormore hydrogen atoms contained in the aromatic hydrocarbon group may bereplaced by a halogen atom, a hydroxy group or a C₁ to C₁₂ alkoxy group;

R^(b7) and R^(b8) in each occurrence independently represent a hydroxygroup, a C₁ to C₁₂ alkyl group or a C₁ to C₁₂ alkoxyl group;

m2 and n2 independently represent an integer of 0 to 5;

R^(b9) and R^(b10) independently represent a C₁ to C₁₈ alkyl group or aC₃ to C₁₈ alicyclic hydrocarbon group, or R^(b9) and R^(b19) may bebonded together with a sulfur atom bonded thereto to form asulfur-containing 3- to 12-membered (preferably 3- to 7-membered) ring,and one or more —CH₂— contained in the ring may be replaced by —O—, —CO—or —S—;

R^(b11) represents a hydrogen atom, a C₁ to C₁₈ alkyl group, a C₃ to C₁₈alicyclic hydrocarbon group or a C₆ to C₁₈ aromatic hydrocarbon group;

R^(b12) represents a C₁ to C₁₂ alkyl group, a C₃ to C₁₈ alicyclichydrocarbon group or a C₆ to C₁₈ aromatic hydrocarbon group, one or morehydrogen atoms contained in the alkyl group may be replaced by a C₁ toC₁₈ aromatic hydrocarbon group, one or more hydrogen atoms contained inthe aromatic hydrocarbon group may be replaced by a C₁ to C₁₂ alkoxygroup or a C₁ to C₁₂ alkyl carbonyloxy group;

R^(b11) and R^(b12) may be bonded together with —CH—CO— bonded theretoto form a 3- to 12-membered (preferably a 3- to 7-membered) ring, andone or more —CH₂— contained in the ring may be replaced by —O—, —CO— or—S—;

R^(b13), R^(b14), R^(b15), R^(b16), R^(b17) and R^(b18) in eachoccurrence independently represent a hydroxy group, a C₁ to C₁₂ alkylgroup or a C₁ to C₁₂ alkoxy group;

L^(b11) represents —S— or —O—;

o2, p2, s2 and t2 independently represent an integer of 0 to 5;

q2 or r2 independently represent an integer of 0 to 4;

u2 represents an integer of 0 or 1.

Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl and 2-ethylhexylgroups. In particular, the alkyl group of R^(b9) to R^(b12) ispreferably a C₁ to C₁₂ alkyl group.

Examples of the alkyl group in which one or more hydrogen atoms arereplaced by an alicyclic hydrocarbon group include1-(1-adamatane-1-yl)-alkane-1-yl group.

Examples of the alicyclic hydrocarbon group include a monocyclichydrocarbon groups such as cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclodecyl; a polycyclic hydrocarbon groupssuch as decahydronaphtyl, adamantyl and norbornyl groups as well asgroups below.

In particular, the alicyclic hydrocarbon group of R^(b9) to R^(b12) ispreferably a C₃ to C₁₈ alicyclic hydrocarbon group, and more preferablya C₄ to C₁₂ alicyclic hydrocarbon group.

Examples of the alicyclic hydrocarbon group in which one or morehydrogen atoms are replaced by an alkyl group include methyl cyclohexyl,dimethyl cyclohexyl, 2-alkyl-2-adamantane-2-yl, methyl norbornyl andisobornyl groups.

Examples of the aromatic hydrocarbon group include phenyl, naphthyl,anthryl, p-methylphenyl, p-tert-butylphenyl, p-adamantylphenyl, tolyl,xylyl, cumenyl, mesityl, biphenyl, phenanthryl, 2,6-diethylphenyl and2-methyl-6-ethylphenyl groups.

When the aromatic hydrocarbon include an alkyl group or an alicyclichydrocarbon group, a C₁ to C₁₈ alkyl group or a C₃ to C₁₈ alicyclichydrocarbon group is preferable.

Examples of the alkyl group in which one or more hydrogen atoms arereplaced by an aromatic hydrocarbon group, i.e., aralkyl group includebenzyl, phenethyl, phenylpropyl, trityl, naphthylmethyl andnaphthylethyl groups.

Examples of the alkoxyl group include methoxy, ethoxy, propoxy, propoxy,butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, decyloxy anddodecyloxy groups.

Examples of the halogen atom include fluorine, chlorine, bromine andiodine atoms.

Examples of the acyl group include acetyl, propionyl and butyryl groups.

Examples of the alkyl carbonyloxy group include methyl carbonyloxy,ethyl carbonyloxy, n-propyl carbonyloxy, isopropyl carbonyloxy, n-butylcarbonyloxy, sec-butyl carbonyloxy, tert-butyl carbonyloxy, pentylcarbonyloxy, hexyl carbonyloxy, octylcarbonyloxy and2-ethylhexylcarbonyloxy groups.

The sulfur-containing ring formed by R^(b4) and R^(b5) may be either ofmonocyclic or polycyclic, aromatic or non-aromatic, or saturated orunsaturated ring, and may further have at least one of sulfur atomand/or at least one of oxygen atom as long as the ring has one sulfuratom. The ring is preferably a ring having 3 to 18 carbon atoms, andmore preferably a ring having 4 to 12 carbon atoms.

Examples of the ring having a sulfur atom and formed by R^(b9) andR^(b10) bonded together include thiolane-1-ium ring(tetrahydrothiophenium ring), thian-1-ium ring and 1,4-oxathian-4-iumring.

Examples of the ring having —CH—CO— and formed by R^(b11) and R^(b12)bonded together include oxocycloheptane ring, oxocyclohexane ring,oxonorbornane ring and oxoadamantane ring.

Among the cations represented by the formula (b2-1) to the formula(b2-4), the cation represented by the formula (b2-1-1) is preferable,and triphenyl sulfonium cation (v2=w2=x2=0 in the formula (b2-1-1)),diphenyl sulfonium cation (v2=w2=0, x2=1, and R^(b21) is a methyl groupin the formula (b2-1-1)), and tritolyl sulfonium cation (v2=w2=x2=1,R^(b19), R^(b20) and R^(b21) are a methyl group in the formula (b2-1-1))are more preferable.

wherein R^(b19), R^(b20) and R^(b21) in each occurrence independentlyrepresent a halogen atom, a hydroxy group, a C₁ to C₁₈ alkyl group, a C₃to C₁₈ alicyclic hydrocarbon group or a C₁ to C₁₂ alkoxy group, or twoof R¹⁹, R^(b20) and R^(b21) may be bonded together to form asulfur-containing ring;

v2 to x2 independently represent an integer of 0 to 5.

In the formula (b2-1-1), the sulfur-containing ring formed by two ofR^(b19), R^(b20) and R^(b21) may be either of monocyclic or polycyclic,aromatic or non-aromatic, or saturated or unsaturated ring, and mayfurther have at least one of sulfur atom and/or at least one of oxygenatom as long as the ring has one sulfur atom.

In particular, the alkyl group of R^(b19) to R^(b21) is preferably a C₁to C₁₂ alkyl group, the alicyclic hydrocarbon group of R^(b19) toR^(b21) is preferably a C₄ to C₁₈ alicyclic hydrocarbon group,

R^(b19) to R^(b21) independently preferably represent a halogen atom(and more preferably fluorine atom), a hydroxy group, a C₁ to C₁₂ alkylgroup or a C₁ to C₁₂ alkoxy group; or two of R^(b19), R^(b20) andR^(b21) preferably are bonded together to form a sulfur-containing ring,and

v2 to x2 independently represent preferably 0 or 1.

Specific examples of the cation of the formula (b2-1-1) include a cationbelow.

Specific examples of the cation of the formula (b2-2) include a cationbelow.

Specific examples of the cation of the formula (b2-3) include a cationbelow.

The acid generator (II) is a compound in combination of the above anionand an organic cation. The above anion and the organic cation mayoptionally be combined, for example, examples thereof include saltsbelow.

The acid generator (II) can be produced by methods described as oraccording to below (1) to (3). In the formula below, s1, t1, s11, t11,s12, t12, R²³, R²⁴, R²⁶, R²⁷, R²⁸, X²¹, u1, u2, u3 and Z¹⁺ have the samedefinition of the above.

(1) An acid generator represented by the formula (IIa) in which X²¹ inthe formula (II) is a group represented by the formula (b1-1), i.e.,—CO—O-L^(b2)- can be produced by reacting a salt represented by theformula (II-1) with a compound represented by the formula (II-2) in asolvent.

Preferred examples of the solvent include acetonitrile.

(2) An acid generator represented by the formula (II-a-a) in which X²¹in the formula (II-a) is a group represented by the formula (b1-1),i.e., −CO—O-L^(b2)- can be produced by reacting a salt represented bythe formula (IIA-1) with a compound represented by the formula (IIA-2)in a solvent.

Preferred examples of the solvent include acetonitrile.

Examples of the compound represented by the formula (IIA-2) includeglycidol, 2-hydroxymethyl oxetane and 3-ethyl-3-oxetane methanol.

The salt represented by the formula (IIA-1) can be obtained by reactinga salt represented by the formula (IIA-3) with a compound represented bythe formula (IIA-4), i.e., carbodiimidazole in a solvent. Preferredexamples of the solvent include acetonitrile.

The compound represented by the formula (IIA-3) can be formed by amethod described in JP2008-127367A.

(3) An acid generator represented by the formula (II-a-b) in which X²¹in the formula (II-a) is a group represented by the formula (b1-2),i.e., —CO—O-L^(b4)-CO—O-L^(b3)- can be produced by reacting a saltrepresented by the formula (IIB-1) with a compound represented by theformula (IIB-2) in a solvent. Preferred examples of the solvent includeacetonitrile.

The compound represented by the formula (IIB-1) can be obtained byreacting a salt represented by the formula (IIB-2) with a compoundrepresented by the formula (IIB-3), i.e., carbodiimidazole in a solvent.Preferred examples of the solvent include acetonitrile.

Examples of the compound represented by the formula (IIB-2) includeglycidol and 2-hydroxymethyl oxetane.

The salt represented by the formula (IIB-2) can be obtained by reactinga salt represented by the formula (IIB-4) with a compound represented bythe formula (IIB-5) in presence of a catalyst in a solvent. Preferredexamples of the solvent include dimethylformamide. Preferred examples ofthe catalyst include potassium carbonate and potassium iodide.

The salt represented by the formula (IIB-4) can be formed by a methoddescribed in JP2008-127367A.

Examples of the compound represented by the formula (IIB-5) includebromo acetic acid.

In the resist composition of the present invention, the acid generator(II) may be used as a single compound or as a combination of two or morecompounds.

<Acid Generator (B)>

The resist composition of the present invention contains at least onekinds of acid generator (II) and may further include a known acidgenerator other than the acid generator (II) (hereinafter is sometimesreferred to as “acid generator (B)”).

An acid generator (B) is classified into non-ionic-based or ionic-basedacid generator.

Examples of the non-ionic-based acid generator include organichalogenated compounds; sulfonate esters such as 2-nitrobenzyl ester,aromatic sulfonate, oxime sulfonate, N-sulfonyl oxyimide, sulfonyloxyketone and diazo naphthoquinone 4-sulfonate; sulfones such asdisulfone, ketosulfone and sulfonyl diazomethane.

Examples of the ionic acid generator includes onium salts containingonium cation (such as diazonium salts, phosphonium salts, sulfoniumsalts, iodonium salts).

Examples of anion of onium salts include sulfonate anion, sulfonylimideanion and sulfonylmethyde anion.

For the acid generator (B), compounds which generate an acid byradiation described in JP S63-26653-A, JP S55-164824-A, JP S62-69263-A,JP S63-146038-A, JP S63-163452-A, JP S62-153853-A, JP 563-146029-A, U.S.Pat. No. 3,779,778-B, U.S. Pat. No. 3,849,137-B, DE3,914,407-B andEP-126,712-A can be used. Also, the acid generator formed according toconventional methods can be used.

A fluorine-containing acid generator is preferable for the acidgenerator (B), and a sulfonic acid salt represented by the formula (B1)is more preferable.

wherein Q¹ and Q² independently represent a fluorine atom or a C₁ to C₆perfluoroalkyl group;

L^(b1) represents a single bond or an C₁ to C₁₇ divalent saturatedhydrocarbon group, and one or more —CH₂— contained in the divalentsaturated hydrocarbon group may be replaced by —O— or —CO—;

Y represents an optionally substituted C₁ to C₁₈ aliphatic hydrocarbongroup or an optionally substituted C₃ to C₁₈ alicyclic hydrocarbongroup, and one or more —CH₂— contained in the aliphatic hydrocarbongroup and alicyclic hydrocarbon group may be replaced by —O—, —CO— or—SO₂—; and

Z⁺ represents an organic cation.

In the formula (B1), a moiety having a negative charge in which anorganic cation, Z⁺, having a positive charge is removed sometimes refersto as a sulfonate anion.

Examples of the perfluoroalkyl group of Q¹ and Q² includetrifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl,perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl,perfluoropentyl and perfluorohexyl groups.

Among these, Q¹ and Q² independently are preferably trifluoromethyl orfluorine atom, and more preferably a fluorine atom.

Examples of the a divalent saturated hydrocarbon group of L^(b1) includeany of;

a chain alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl,heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl,undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl,tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl,heptadecane-1,17-diyl, ethane-1,1-diyl, propan-1,1-diyl andpropan-2,2-diyl groups;

a branched chain alkanediyl group such as a group in which a chainalkanediyl group is bonded a side chain of a C₁ to C₄ alkyl group suchas methyl, ethyl, propyl, isopropyl, butyl, sec-butyl and tert-butyl,for example, butane-1,3-diyl, 2-methylpropane-1,3-diyl,2-methylpropane-1,2-diyl, pentane-1,4-diyl and 2-methylbutane-1,4-diylgroups;

a mono-alicyclic saturated hydrocarbon group such as a cycloalkanediylgroup (e.g., cyclobutan-1,3-diyl, cyclopentan-1,3-diyl,cyclohexane-1,4-diyl and cyclooctan-1,5-diyl groups);

a poly-alicyclic saturated hydrocarbon group such asnorbornane-2,3-diyl, norbornane-1,4-diyl, norbornane-2,5-diyl,adamantane-1,5-diyl and adamantane-2,6-diyl groups; and

a combination of two or more groups.

Examples of the saturated hydrocarbon group of L^(b1) in which one ormore —CH₂— contained in the saturated hydrocarbon group is replaced by—O— or —CO— include groups represented by the formula (b1-1) to theformula (b1-6) as described above.

Examples of the aliphatic hydrocarbon group of Y include an alkyl groupsuch as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,2-ethylhexyl, octyl, nonyl, decyl, undecyl and dodecyl groups, and a C₁to C₆ alkyl group is preferable.

Examples of the alicyclic hydrocarbon group of Y include groupsrepresented by the formula (Y1) to the formula (Y11).

Examples of the alicyclic hydrocarbon group of Y in which one or more—CH₂— contained in the alicyclic hydrocarbon group is replaced by —O—,—CO— or —SO₂— include groups represented by the formula (Y12) to theformula (Y26).

Among these, the alicyclic hydrocarbon group is preferably any one ofgroups represented by the formula (Y1) to the formula (Y19), morepreferably any one of groups represented by the formula (Y11), (Y14),(Y15) or (Y19), and still more preferably group represented by theformula (Y11) or (Y14).

Y may have a substituent.

Examples of the substituent of Y include a halogen atom, a hydroxygroup, a C₁ to C₁₂ alkyl group, a hydroxy group-containing C₁ to C₁₂alkyl group, a C₃ to C₁₆ alicyclic hydrocarbon group, a C₁ to C₁₂ alkoxygroup, a C₆ to C₁₈ aromatic hydrocarbon group, a C₇ to C₂₁ aralkylgroup, a C₂ to C₄ acyl group, a glycidyloxy group or a—(CH₂)_(j2)—O—CO—R^(b1) group, wherein R^(b1) represents a C₁ to C₁₆alkyl group, a C₃ to C₁₆ alicyclic hydrocarbon group or a C₆ to C₁₈aromatic hydrocarbon group, j2 represents an integer of 0 to 4. Thealkyl group, alicyclic hydrocarbon group, aromatic hydrocarbon group andthe aralkyl group of the substituent may further have a substituent suchas a C₁ to C₆ alkyl group, a halogen atom and a hydroxy group.

Examples of the halogen atom include fluorine, chlorine, bromine andiodine atoms.

Examples of the hydroxy group-containing alkyl group includehydroxymethyl and hydroxyethyl groups

Examples of the alkoxyl group include methoxy, ethoxy, n-propoxy,isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentyloxy andn-hexyloxy groups.

Examples of the aromatic hydrocarbon group include an aryl group such asphenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl,p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl,phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the aralkyl group include benzyl, phenethyl, phenylpropyl,naphthylmethyl and naphthylethyl groups.

Examples of the acyl group include acetyl, propionyl and butyryl groups.

Examples of the alkyl and the alicyclic hydrocarbon groups are the sameexamples as described above.

Examples of Y include the groups below.

When Y represents an alkyl group and L^(b1) represents a C₁ to C₁₇divalent saturated hydrocarbon group, the —CH₂— contained in thedivalent saturated hydrocarbon group bonding Y is preferably replaced byan oxygen atom or carbonyl group. In this case, the —CH₂— contained inthe alkyl group constituting Y is not replaced by an oxygen atom orcarbonyl group. The same shall be applied when the alkyl group of Y anddivalent saturated hydrocarbon group of L^(b1) has a substituent.

Y is preferably an alicyclic hydrocarbon group which may optionally havea substituent, more preferably an adamantyl group which may optionallyhave a substituent, for example, an oxo group and a hydroxy group, andstill more preferably an adamantyl group, a hydroxyadamantyl group andan oxoadamantyl group.

The sulfonate anion is preferably an anions represented by the formula(b1-1-1) to the formula (b1-1-9) below. In the formula (b1-1-1) to theformula (b1-1-9), Q¹, Q² and L^(b2) represents the same meaning asdefined above. R^(b2) and R^(b3) independently represent a C₁ to C₄alkyl group (preferably methyl group).

Specific examples of the sulfonate anion include sulfonate anionsdescribed in JP2010-204646A.

Examples of the cation of the acid generator (B) include an organiconium cation, for example, organic sulfonium cation, organic iodoniumcation, organic ammonium cation, benzothiazolium cation and organicphosphonium cation. Among these, organic sulfonium cation and organiciodonium cation are preferable, and aryl sulfonium cation is morepreferable.

Z⁺ of the formula (B1) includes cations represented by the formula(b2-1) to the formula (b2-4) as described above.

Preferred acid generators (B1) are represented by the formula (B1-1) tothe formula (B1-20). Among these, the formulae (B1-1), (B1-2), (B1-6),(B1-11), (B1-12), (B1-13) and (B1-14) which contain triphenyl sulfoniumcation, and the formulae (B1-3) and (B1-7) which contain tritolylsulfonium cation are preferable.

In the resist composition of the present invention, the acid generator(B) may be used as a single salt or as a combination of two or moresalts.

In the resist composition of the present invention, the proportion ofthe acid generator (II) is preferably not less than 1 weight % (and morepreferably not less than 3 weight %), and not more than 30 weight % (andmore preferably not more than 25 weight %), with respect to the resin(A2).

When the resist composition of the present invention include the acidgenerator (B1) in addition to the acid generator (II), the totalproportion hereof is preferably not less than 1 weight % (and morepreferably not less than 3 weight %), and not more than 40 weight % (andmore preferably not more than 35 weight %, and still more preferably notmore than 30 weight %), with respect to the resin (A2). In this case,the weight ratio of the acid generator (II) and the acid generator (B)is preferably, for example, 5:95 to 95:5, more preferably 10:90 to 90:10and still more preferably 15:85 to 85:15.

<Solvent (E)>

The resist composition of the present invention preferably includes asolvent (E). The proportion of the solvent (E) 90 weight % or more,preferably 92 weight % or more, and more preferably 94 weight % or more,and also preferably 99.9 weight % or less and more preferably 99 weight% or less. The proportion of the solvent (E) can be measured with aknown analytical method such as, for example, liquid chromatography andgas chromatography.

Examples of the solvent (E) include glycol ether esters such asethylcellosolve acetate, methylcellosolve acetate and propylene glycolmonomethyl ether acetate; glycol ethers such as propylene glycolmonomethyl ether; ethers such as diethylene glycol dimethyl ether;esters such as ethyl lactate, butyl acetate, amyl acetate and ethylpyruvate; ketones such as acetone, methyl isobutyl ketone, 2-heptanoneand cyclohexanone; and cyclic esters such as γ-butyrolactone. Thesesolvents may be used as a single solvent or as a mixture of two or moresolvents.

<Basic Compound (C)>

The resist composition of the present invention may contain a basiccompound (C). The basic compound (C) is a compound having a property toquench an acid, in particular, generated from the acid generator (B),and called “quencher”.

As the basic compounds (C), nitrogen-containing basic compounds (forexample, amine and basic ammonium salt) are preferable. The amine may bean aliphatic amine or an aromatic amine. The aliphatic amine includesany of a primary amine, secondary amine and tertiary amine. The aromaticamine includes an amine in which an amino group is bonded to an aromaticring such as aniline, and a hetero-aromatic amine such as pyridine.

Preferred basic compounds (C) include compounds presented by the formula(C1) to the formula (C8) and the formula (C1-1) as described below.Among these, the basic compound presented by the formula (C1-1) is morepreferable.

wherein R^(c1), R^(c2) and R^(c3) independently represent a hydrogenatom, a C₁ to C₆ alkyl group, C₅ to C₁₀ alicyclic hydrocarbon group or aC₆ to C₁₀ aromatic hydrocarbon group, one or more hydrogen atomcontained in the alkyl group and alicyclic hydrocarbon group may bereplaced by a hydroxy group, an amino group or a C₁ to C₆ alkoxyl group,one or more hydrogen atom contained in the aromatic hydrocarbon groupmay be replaced by a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxyl group, aC₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀ aromatichydrocarbon group.

wherein R^(c2) and R^(c3) have the same definition of the above;

R^(c4) in each occurrence represents a C₁ to C₆ alkyl group, a C₁ to C₆alkoxyl group, a C₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀aromatic hydrocarbon group;

m3 represents an integer 0 to 3.

wherein R^(c5), R^(c6), R^(c7) and R^(c8) independently represent theany of the group as described in R^(c1) of the above;

R^(c9) in each occurrence independently represents a C₁ to C₆ alkylgroup, a C₃ to C₆ alicyclic hydrocarbon group or a C₂ to C₆ alkanoylgroup;

n3 represents an integer of 0 to 8.

wherein R^(c10), R^(c11), R^(c12), R^(c13) and R^(c16) independentlyrepresent the any of the groups as described in R^(c1);

R^(c14), R^(c15) and R^(c17) in each occurrence independently representthe any of the groups as described in R^(c4);

o3 and p3 represent an integer of 0 to 3;

L^(c1) represents a divalent C₁ to C₆ alkanediyl group, —CO—, —C(═NH)—,—S— or a combination thereof.

wherein R^(c18), R^(c19) and R^(c20) in each occurrence independentlyrepresent the any of the groups as described in R^(c4);

q3, r3 and s3 represent an integer of 0 to 3;

L^(c2) represents a single bond, a C₁ to C₆ alkanediyl group, —CO—,—C(═NH)—, —S— or a combination thereof.

In the formula (C1) to the formula (C8) and the formula (C1-1), thealkyl, alicyclic hydrocarbon, aromatic, alkoxy and alkanediyl groupsinclude the same examples as the above.

Examples of the alkanoyl group include acetyl, 2-methyl acetyl,2,2-dimethyl acetyl, propionyl, butyryl, isobutyryl, pentanoyl and2,2-dimethyl propionyl groups.

Specific examples of the amine represented by the formula (C1) include1-naphtylamine, 2-naphtylamine, aniline, diisopropylaniline, 2-, 3- or4-methylaniline, 4-nitroaniline, N-methylaniline, N,N-dimethylaniline,diphenylamine, hexylamine, heptylamine, octylamine, nonylamine,decylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine,dioctylamine, dinonylamine, didecylamine, triethylamine, trimethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine,methyldibutylamine, methyldipentylamine, methyldihexylamine,methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine,methyldinonylamine, methyldidecylamine, ethyldibutylamine,ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine,ethyldioctylamine, ethyldinonylamine, ethyldidecylamine,dicyclohexylmethylamine, tris[2-(2-methoxyethoxy)ethyl]amine,triisopropanolamine, ethylene diamine, tetramethylene diamine,hexamethylene diamine, 4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane and4,4′-diamino-3,3′-diethyldiphenylmethane.

Among these, diisopropylaniline is preferable, particularly2,6-diisopropylaniline is more preferable as the basic compounds (C)contained in the present resist composition.

Specific examples of the compound represented by the formula (C2)include, for example, piperazine.

Specific examples of the compound represented by the formula (C3)include, for example, morpholine.

Specific examples of the compound represented by the formula (C4)include, for example, piperidine, a hindered amine compound havingpiperidine skeleton described in JP H11-52575-A.

Specific examples of the compound represented by the formula (C5)include, for example, 2,2′-methylenebisaniline.

Specific examples of the compound represented by the formula (C6)include, for example, imidazole and 4-methylimidazole.

Specific examples of the compound represented by the formula (C7)include, for example, pyridine and 4-methylpyridine.

Specific examples of the compound represented by the formula (C8)include, for example, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene,1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane,di(2-pyridyl)ketone, 4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide,2,2′-dipyridylamine, 2,2′-dipicolylamine and bipyridine.

Examples of the ammonium salt include tetramethylammonium hydroxide,tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethyl ammonium hydroxide, 3-(trifluoromethyl)phenyltrimethylammonium hydroxide, tetra-n-butyl ammonium salicylate andcholine.

The proportion of the basic compound (C) is preferably 0.01 to 5 weight%, more preferably 0.01 to 3 weight %, and still more preferably 0.01 to1 weight % with respect to the total solid proportion of the resistcomposition.

<Other Ingredient (Hereinafter is Sometimes Referred to as “OtherIngredient (F)”>

The resist composition can also include small amounts of various knownadditives such as sensitizers, dissolution inhibitors, surfactants,stabilizers, and dyes, as needed.

<Preparing the Resist Composition>

The present resist composition can be prepared by mixing the resin (A1),the resin (A2) and the acid generator (II), and the basic compound (C),the solvent (E), the acid generator (B) and the other ingredient (F) asneeded. There is no particular limitation on the order of mixing. Themixing may be performed in an arbitrary order. The temperature of mixingmay be adjusted to an appropriate temperature within the range of 10 to40° C., depending on the kinds of the resin and solubility in thesolvent (E) of the resin. The time of mixing may be adjusted to anappropriate time within the range of 0.5 to 24 hours, depending on themixing temperature. There is no particular limitation to the tool formixing. An agitation mixing may be adopted.

After mixing the above ingredients, the present resist compositions canbe prepared by filtering the mixture through a filter having about 0.003to 0.2 μm pore diameter.

<Method for Producing a Resist Pattern>

The method for producing a resist pattern of the present inventionincludes the steps of:

(1) applying the resist composition of the present invention onto asubstrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

Applying the resist composition onto the substrate can generally becarried out through the use of a resist application device, such as aspin coater known in the field of semiconductor microfabricationtechnique.

Drying the applied composition layer, for example, can be carried outusing a heating device such as a hotplate (so-called “prebake”), adecompression device, or a combination thereof. Thus, the solventevaporates from the resist composition and a composition layer with thesolvent removed is formed. The condition of the heating device or thedecompression device can be adjusted depending on the kinds of thesolvent used. The temperature in this case is generally within the rangeof 50 to 200° C. Moreover, the pressure is generally within the range of1 to 1.0×10⁵ Pa.

The composition layer thus obtained is generally exposed using anexposure apparatus or a liquid immersion exposure apparatus. Theexposure is generally carried out through a mask that corresponds to thedesired pattern. Various types of exposure light source can be used,such as irradiation with ultraviolet lasers such as KrF excimer laser(wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm), F₂ excimerlaser (wavelength: 157 nm), or irradiation with far-ultravioletwavelength-converted laser light from a solid-state laser source (YAG orsemiconductor laser or the like), or vacuum ultraviolet harmonic laserlight or the like. Also, the exposure device may be one which irradiateselectron beam or extreme-ultraviolet light (EUV).

After exposure, the composition layer is subjected to a heat treatment(so-called “post-exposure bake”) to promote the deprotection reaction.The heat treatment can be carried out using a heating device such as ahotplate. The heating temperature is generally in the range of 50 to200° C., preferably in the range of 70 to 150° C.

The composition layer is developed after the heat treatment, generallywith an alkaline developing solution and using a developing apparatus.The development here means to bring the composition layer after the heattreatment into contact with an alkaline solution. Thus, the exposedportion of the composition layer is dissolved by the alkaline solutionand removed, and the unexposed portion of the composition layer remainson the substrate, whereby producing a resist pattern. Here, as thealkaline developing solution, various types of aqueous alkalinesolutions used in this field can be used. Examples include aqueoussolutions of tetramethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (common name: choline).

After the development, it is preferable to rinse the substrate and thepattern with ultrapure water and to remove any residual water thereon.

<Application>

The resist composition of the present invention is useful as the resistcomposition for excimer laser lithography such as with ArF, KrF or thelike, and the resist composition for electron beam (EB) exposurelithography and extreme-ultraviolet (EUV) exposure lithography, as wellas liquid immersion exposure lithography.

The resist composition of the present invention can be used insemiconductor microfabrication and in manufacture of liquid crystals,thermal print heads for circuit boards and the like, and furthermore inother photofabrication processes, which can be suitably used in a widerange of applications.

EXAMPLES

The present invention will be described more specifically by way ofexamples, which are not construed to limit the scope of the presentinvention.

All percentages and parts expressing the content or amounts used in theExamples and Comparative Examples are based on weight, unless otherwisespecified.

The structure of a compound is measured by MASS (LC: manufactured byAgilent, 1100 type, MASS: manufactured by Agilent, LC/MSD type or LC/MSDTOF type).

The weight average molecular weight is a value determined by gelpermeation chromatography.

Apparatus: HLC-8120GPCtype (Tosoh Co. Ltd.)

Column: TSK gel Multipore HXL-M×3+guardcolumn (Tosoh Co. Ltd.)

Eluant: tetrahydrofuran

Flow rate: 1.0 mL/min

Detecting device: RI detector

Column temperature: 40° C.

Injection amount: 100 μL

Standard material for calculating molecular weight: standard polystylene(Toso Co. ltd.)

Synthesis Example 1 Synthesis of Compound Represented by the Formula (A)

9.60 parts of a compound (A-2), 38.40 parts of tetrahydrofuran and 5.99parts of pyridine were mixed, and stirred for 30 minutes at 23° C. Theobtained mixture was cooled to 0° C. To this mixture, 14.00 parts of acompound (A-1) was added over 1 hour while maintaining at the sametemperature. The temperature of the mixture was then elevated to about10° C., and the mixture was stirred for 1 hour at the same temperature.To the obtained reactant including a compound (A-3), 14.51 parts of acompound of (A-4), 1-(3-dimethylaminopropyl)-3-ethyl carbodiimidehydrochloride, and 8.20 parts of a compound of (A-5) were added, andstirred for 3 hours at 23° C. 271.95 parts of ethyl acetate and 16.57parts of 5% of hydrochloric acid solution were added to the obtainedmixture, the mixture was stirred for 30 minutes at 23° C. The obtainedsolution was allowed to stand, and then separated to recover an organiclayer. To the recovered organic layer, 63.64 parts of a saturated sodiumhydrogen carbonate was added, and the obtained solution was stirred for30 minutes at 23° C., allowed to stand, and then separated to wash theorganic layer. These washing operations were repeated for 2 times. Tothe washed organic layer, 67.99 parts of ion-exchanged water was added,and the obtained solution was stirred for 30 minutes at 23° C., allowedto stand, and then separated to wash the organic layer with water. Thesewashing operations were repeated for 5 times. The obtained organic layerwas concentrated, to the obtained concentrate, 107.71 parts of ethylacetate was added, stirred to dissolve the concentrate completely, and64.26 parts of n-heptane was added in the form of drops to this. Afteraddition, the obtained mixture was stirred for 30 minutes at 23° C., andfiltrated, resulting in 15.11 parts of the compound (A).

MS (mass spectroscopy): 486.2 (molecular ion peak)

Synthesis Example 2 Synthesis of Compound Represented by the Formula (B)

6.32 parts of a compound (B-2), 30.00 parts of tetrahydrofuran and 5.99parts of pyridine were mixed, and stirred for 30 minutes at 23° C. Theobtained mixture was cooled to 0° C. To this mixture, 14.00 parts of acompound (B-1) was added over 1 hour while maintaining at the sametemperature. The temperature of the mixture was then elevated to about10° C., and the mixture was stirred for 1 hour at the same temperature.To the obtained reactant including a compound (B-3), 14.51 parts of acompound of (B-4), 1-(3-dimethylaminopropyl)-3-ethyl carbodiimidehydrochloride, and 8.20 parts of a compound of (B-5) were added, andstirred for 3 hours at 23° C. 270.00 parts of ethyl acetate and 16.57parts of 5% of hydrochloric acid solution were added to the obtainedmixture, the mixture was stirred for 30 minutes at 23° C. The obtainedsolution was allowed to stand, and then separated to recover an organiclayer. To the recovered organic layer, 65.00 parts of a saturated sodiumhydrogen carbonate was added, and the obtained solution was stirred for30 minutes at 23° C., allowed to stand, and then separated to wash theorganic layer. These washing operations were repeated for 2 times. Tothe washed organic layer was added 65.00 parts of ion-exchanged water,and the obtained solution was stirred for 30 minutes at 23° C., allowedto stand, and then separated to wash the organic layer with water. Thesewashing operations were repeated for 5 times. The obtained organic layerwas concentrated, to the obtained concentrate, and separated by a column(condition; stationary phase: silica gel 60-200 mesh manufactured byMerk, developing solvent: n-heptane/ethyl acetate), resulting in 9.90parts of the compound (B).

MS (mass spectroscopy): 434.1 (molecular ion peak)

Synthesis Example 3 Synthesis of Compound Represented by the Formula (C)

7.08 parts of a compound (C-2), 30.00 parts of tetrahydrofuran and 5.99parts of pyridine were mixed, and stirred for 30 minutes at 23° C. Theobtained mixture was cooled to 0° C. To this mixture, 14.00 parts of acompound (C-1) was added over 1 hour while maintaining at the sametemperature. The temperature of the mixture was then elevated to about10° C., and the mixture was stirred for 1 hour at the same temperature.To the obtained reactant including a compound (C-3), 14.51 parts of acompound of (C-4), 1-(3-dimethylaminopropyl)-3-ethyl carbodiimidehydrochloride, and 8.20 parts of a compound of (C-5) were added, andstirred for 3 hours at 23° C. 270.00 parts of ethyl acetate and 16.57parts of 5% of hydrochloric acid solution were added to the obtainedmixture, the mixture was stirred for 30 minutes at 23° C. The obtainedsolution was allowed to stand, and then separated to recover an organiclayer. To the recovered organic layer, 65.00 parts of a saturated sodiumhydrogen carbonate was added, and the obtained solution was stirred for30 minutes at 23° C., allowed to stand, and then separated to wash theorganic layer. These washing operations were repeated for 2 times. Tothe washed organic layer was added 65.00 parts of ion-exchanged water,and the obtained solution was stirred for 30 minutes at 23° C., allowedto stand, and then separated to wash the organic layer with water. Thesewashing operations were repeated for 5 times. The obtained organic layerwas concentrated, to the obtained concentrate, and separated by a column(condition; stationary phase: silica gel 60-200 mesh manufactured byMerk, developing solvent: n-heptane/ethyl acetate), resulting in 10.24parts of the compound (C).

MS (mass spectroscopy): 446.1 (molecular ion peak)

Synthesis Example 4 Synthesis of Compound Represented by the Formula (E)

25 parts of a compound (E-1) and 25 parts of tetrahydrofuran were mixed,and stirred for 30 minutes at 23° C. The obtained mixture was cooled to0° C. To this mixture, 10.2 parts of a compound (E-2), 11.2 parts ofpyridine and 30 parts of tetrahydrofuran were added over 1 hour whilemaintaining at the same temperature. The temperature of the mixture wasthen elevated to about 25° C., and the mixture was stirred for 1 hour atthe same temperature. To the obtained reactant, 200 parts of ethylacetate and 50 parts of ion-exchanged-water were added, stirred, andthen separated to recover an organic layer. The obtained organic layerwas concentrated, to this concentrate, 500 parts of n-heptane was addedto obtain a solution, and the solution was stirred and filtrated,resulting in 40.18 parts of a compound (E-3). 35.21 parts of thecompound (E-3), 160 parts of tetrahydrofuran, 22.8 parts of the compound(E-5) and 8.3 parts of pyridine were charged, and stirred for 30 minutesat 23° C. The obtained mixture was cooled to 0° C. To the obtainedmixture, 33.6 parts of a compound of (E-4),1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride, and 140parts of chloroform were added, and stirred for 18 hours at 23° C. Tothis reactant solution, 850 parts of n-heptane and 77 parts of 5% ofhydrochloric acid solution were added, the mixture was stirred for 30minutes at 23° C. The obtained solution was allowed to stand, and thenseparated to recover an organic layer. To the recovered organic layer,61 parts of 10% potassium carbonate was added, and the obtained solutionwas stirred for 30 minutes at 23° C., allowed to stand, and thenseparated to wash the organic layer. These washing operations wererepeated for 2 times. To the washed organic layer, 230 parts ofion-exchanged water was added, and the obtained solution was stirred for30 minutes at 23° C., allowed to stand, and then separated to wash theorganic layer with water. These washing operations were repeated for 5times. The obtained organic layer was concentrated, resulting in 31.5parts of the compound (E).

MS (mass spectroscopy): 420.1 (molecular ion peak)

Synthesis Example 5 Synthesis of Compound Represented by the Formula (F)

25.00 parts of a compound (F-1) and 25.00 parts of tetrahydrotetrahydrofuran were mixed, and stirred for 30 minutes at 23° C. Theobtained mixture was cooled to 0° C. To this mixture, a mixture of 8.50parts of a compound (F-2), 25.00 parts of tetrahydrofuran and 11.2 partsof pyridine was added, over 1 hour while maintaining at the sametemperature. The temperature of the mixture was then elevated to about25° C., and the mixture was stirred for 1 hour at the same temperature.To the obtained reactant, 190 parts of ethyl acetate and 50 parts ofion-exchanged water were added, and then separated to recover an organiclayer. The obtained organic layer was concentrated. To the obtainedconcentrate, 150.0 parts of n-heptane was added, and the obtainedmixture was stirred, and the supernatant was removed. The obtainedmixture was concentrated, resulting in 28.7 parts of the compound (F-3).

19.80 parts of a compound (F-3), 90.0 parts of tetrahydrofuran, 10.3parts of a compound (F-5) and 5.0 parts of pyridine were mixed, andstirred for 30 minutes at 23° C. The obtained mixture was cooled to 0°C. To this mixture, 15.2 parts of a compound (F-4),1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride, was added,and stirred for 18 hours at 23° C. 450.0 parts of n-heptane and 47.0parts of 5% of hydrochloric acid solution were added to the obtainedmixture, the mixture was stirred for 30 minutes at 23° C. The obtainedsolution was allowed to stand, and then separated to recover an organiclayer. To the recovered organic layer, 37.0 parts of 10% potassiumcarbonate was added, and the obtained solution was stirred for 30minutes at 23° C., allowed to stand, and then separated to wash theorganic layer. These washing operations were repeated for 2 times. Tothe washed organic layer, 120.0 parts of ion-exchanged water was added,and the obtained solution was stirred for 30 minutes at 23° C., allowedto stand, and then separated to wash the organic layer with water. Thesewashing operations were repeated for 5 times. The obtained organic layerwas concentrated to the obtained concentrate, resulting in 20.1 parts ofthe compound (F).

MS (mass spectroscopy): 406.1 (molecular ion peak)

Synthesis Example 6 Synthesis of a Salt Represented by the Formula(II-1)

A salt represented by the formula (II-1-a) was synthesized by the methoddescribed in JP2008-127367A.

10.00 parts of the compound represented by the formula (II-1-a), 50.00parts of acetonitrile and 4.44 parts of the compound represented by theformula (II-1-b) (Trade name: carbodiimidazole, Tokyo Chemical IndustryCo., LTD) were charged, and stirred for 30 minutes at 80° C. After that,the obtained reactant was cooled to 23° C., and filtrated, wherebygiving 59.48 parts of the salt represented by the formula (II-1-c).

59.48 parts of the salt represented by the formula (II-1-c) and 2.57parts of a compound represented by the formula (II-1-d) (Trade name:3-ethyl-oxetane methanol, Tokyo Chemical Industry Co., LTD) werecharged, stirred for 1 hour at 23° C., and filtrated. The obtainedfiltrate was concentrated, to this concentrate, 100 parts of chloroformand 30 parts of ion-exchanged water were charged, stirred for 30minutes, and separated to obtain an organic layer. These washing withwater operations were repeated for 3 times. The obtained organic layerwas concentrated to obtain a concentrate, whereby giving 8.73 parts ofthe salt represented by the formula (II-1).

MS (ESI(+) Spectrum): M⁺ 263.1

MS (ESI(−) Spectrum): M⁻ 273.0

Synthesis Example 7 Synthesis of a Salt Represented by the Formula(II-2)

10.96 parts of a salt represented by the formula (II-2-a), 50.00 partsof acetonitrile and 4.44 parts of the compound represented by theformula (II-2-b) (Trade name: carbodiimidazole, Tokyo Chemical IndustryCo., LTD) were charged, and stirred for 30 minutes at 80° C. After that,the obtained reactant was cooled to 23° C., and filtrated, wherebygiving 60.54 parts of the salt represented by the formula (II-2-c).

60.54 parts of the salt represented by the formula (II-2-c) and 2.57parts of a compound represented by the formula (II-2-d) (Trade name:3-ethyl-oxetane methanol, Aldrich Corporation) were charged, stirred for1 hour at 23° C., and filtrated. The obtained filtrate was concentrated,to this concentrate, 100 parts of chloroform and 30 parts ofion-exchanged water were charged, stirred for 30 minutes, and separatedto obtain an organic layer. These washing with water operations wererepeated for 3 times. The obtained organic layer was concentrated toobtain a concentrate, whereby giving 8.92 parts of the salt representedby the formula (II-2).

MS (ESI(+) Spectrum): M⁺ 305.1

MS (ESI(−) Spectrum): M⁻ 273.0

Synthetic Example of the Resin

The monomers used the synthesis of the resin are shown below.

These monomers are referred to as “monomer (a1-1-1)” to “monomer (F)”.

Synthetic Example 8 Synthesis of Resin A1-1

Monomer (a-4-1-7) and monomer (A) were mixed together with a mole ratioof Monomer (a4-1-7): monomer (A)=90:10, and dioxane was added thereto inan amount equal to 1.5 times by weight of the total amount of monomersto obtain a solution. Azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain asolution in an amount of 0.7 mol % and 2.1 mol % respectively withrespect to the entire amount of monomers, and the resultant mixture washeated for about 5 hours at 75° C. After that, the obtained reactedmixture was poured into a large amount of methanol/water mixed solventto precipitate a resin. The obtained resin was filtrated. Thus obtainedresin was dissolved in another dioxane to obtain a solution, and thesolution was poured into a mixture of methanol/water mixed solvent toprecipitate a resin. The obtained resin was filtrated. These operationswere repeated for two times, resulting in a 82% yield of copolymerhaving a weight average molecular weight of about 17000. This copolymer,which had the structural units of the following formula, was referred toResin A1-1.

Synthetic Example 9 Synthesis of Resin A1-2

Monomer (B) was used, and dioxane was added thereto in an amount equalto 1.5 times by weight of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)was added as an initiator to obtain a solution in an amount of 0.7 mol %and 2.1 mol % respectively with respect to the entire amount ofmonomers, and the resultant mixture was heated for about 5 hours at 75°C. After that, the obtained reacted mixture was poured into a largeamount of methanol/water mixed solvent to precipitate a resin. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a mixture of methanol/water mixedsolvent to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated for two times, resulting in a 85% yield ofpolymer having a weight average molecular weight of about 20000. Thispolymer, which had the structural units of the following formula, wasreferred to Resin A1-2.

Synthetic Example 10 Synthesis of Resin A1-3

Monomer (C) was used, and dioxane was added thereto in an amount equalto 1.5 times by weight of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)was added as an initiator to obtain a solution in an amount of 0.7 mol %and 2.1 mol % respectively with respect to the entire amount ofmonomers, and the resultant mixture was heated for about 5 hours at 75°C. After that, the obtained reacted mixture was poured into a largeamount of methanol/water mixed solvent to precipitate a resin. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a mixture of methanol/water mixedsolvent to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated for two times, resulting in a 83% yield ofpolymer having a weight average molecular weight of about 19000. Thispolymer, which had the structural units of the following formula, wasreferred to Resin A1-3.

Synthetic Example 11 Synthesis of Resin A1-4

Monomer (E) was used, and dioxane was added thereto in an amount equalto 1.2 times by weight of the total amount of monomers to obtain asolution. Azobis(2,4-dimethylvaleronitrile) was added as an initiator toobtain a solution in an amount of 4.5 mol % with respect to the entireamount of monomers, and the resultant mixture was heated for about 5hours at 60° C. After that, the obtained reacted mixture was poured intoa large amount of n-heptane to precipitate a resin. The obtained resinwas filtrated, resulting in a 89% yield of polymer having a weightaverage molecular weight of about 26000. This polymer, which had thestructural units of the following formula, was referred to Resin A1-4.

Synthetic Example 12 Synthesis of Resin A1-5

Monomer (F) was used, and dioxane was added thereto in an amount equalto 1.2 times by weight of the total amount of monomers to obtain asolution. Azobis(2,4-dimethylvaleronitrile) was added as an initiator toobtain a solution in an amount of 4.5 mol % with respect to the entireamount of monomers, and the resultant mixture was heated for about 5hours at 60° C. After that, the obtained reacted mixture was poured intoa large amount of n-heptane to precipitate a resin. The obtained resinwas filtrated, resulting in a 90% yield of polymer having a weightaverage molecular weight of about 39000. This polymer, which had thestructural units of the following formula, was referred to Resin A1-5.

Synthetic Example 13 Synthesis of Resin A2-1

Monomer (a1-1-3), monomer (a1-2-3), monomer (a2-1-1), monomer (a3-1-1)and monomer (a3-2-3) were charged with molar ratio 30:14:6:20:30, anddioxane was added thereto in an amount equal to 1.5 weight times of thetotal amount of monomers to obtain a solution. Azobisisobutyronitrileand azobis(2,4-dimethylvaleronitrile) was added as an initiator theretoin an amount of 1 mol % and 3 mol % respectively with respect to theentire amount of monomers, and the resultant mixture was heated forabout 5 hours at 73° C. After that, the reaction solution was pouredinto a mixture of methanol and ion-exchanged water (4:1) in largeamounts to precipitate a resin. The obtained resin was filtrated. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a large amount of a mixture of methanoland water to precipitate a resin. The obtained resin was filtrated.These operations were repeated two times for purification, resulting in65% yield of copolymer having a weight average molecular weight of about8100. This copolymer, which had the structural units derived from themonomers of the following formula, was designated Resin A2-1.

Synthetic Example 14 Synthesis of Resin A2-2

Monomer (a1-1-2), monomer (a1-2-3), monomer (a2-1-1), monomer (a3-1-1)and monomer (a3-2-3) were charged with molar ratio 30:14:6:20:30, anddioxane was added thereto in an amount equal to 1.5 weight times of thetotal amount of monomers to obtain a solution. Azobisisobutyronitrileand azobis(2,4-dimethylvaleronitrile) was added as an initiator theretoin an amount of 1 mol % and 3 mol % respectively with respect to theentire amount of monomers, and the resultant mixture was heated forabout 5 hours at 73° C. After that, the reaction solution was pouredinto a mixture of methanol and ion-exchanged water (4:1) in largeamounts to precipitate a resin. The obtained resin was filtrated. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a large amount of a mixture of methanoland water to precipitate a resin. The obtained resin was filtrated.These operations were repeated two times for purification, resulting in68% yield of copolymer having a weight average molecular weight of about7800. This copolymer, which had the structural units derived from themonomers of the following formula, was designated Resin A2-2.

Synthetic Example 15 Synthesis of Resin A2-3

Monomer (a1-1-2), monomer (a2-1-1) and monomer (a3-1-1) were mixed withmolar ratio 50:25:25, and dioxane was added thereto in an amount equalto 1.5 weight times of the total amount of monomers.Azobisisobutyronitrile and azobis(2,4-dimethyl valeronitrile) was addedas an initiator thereto in an amount of 1 mol % and 3 mol % respectivelywith respect to the entire amount of monomers, and the resultant mixturewas heated for about 8 hours at 80° C. After that, the reaction solutionwas poured into a mixture of methanol and ion-exchanged water (4:1) inlarge amounts to precipitate a resin. The obtained resin was filtrated.Thus obtained resin was dissolved in another dioxane to obtain asolution, and the solution was poured into a large amount of a mixtureof methanol and water to precipitate a resin. The obtained resin wasfiltrated. These operations were repeated three times for purification,resulting in 60% yield of copolymer having a weight average molecularweight of about 9200. This copolymer, which had the structural unitsderived from the monomers of the following formulae, was designatedResin A2-3.

Synthetic Example 16 Synthesis of Resin A2-4

Monomer (a1-1-2), monomer (a1-2-3), monomer (a2-1-1), monomer (a3-2-3)and monomer (a3-1-1) were charged with molar ratio 30:14:6:20:30, anddioxane was added thereto in an amount equal to 1.5 weight times of thetotal amount of monomers to obtain a solution. Azobisisobutyronitrileand azobis(2,4-dimethylvaleronitrile) was added as an initiator theretoin an amount of 1 mol % and 3 mol % respectively with respect to theentire amount of monomers, and the resultant mixture was heated forabout 5 hours at 75° C. After that, the reaction solution was pouredinto a mixture of methanol and ion-exchanged water (4:1) in largeamounts to precipitate a resin. The obtained resin was filtrated. Thusobtained resin was dissolved in another dioxane to obtain a solution,and the solution was poured into a large amount of a mixture of methanoland water to precipitate a resin. The obtained resin was filtrated.These operations were repeated two times for purification, resulting in78% yield of copolymer having a weight average molecular weight of about7200. This copolymer, which had the structural units derived from themonomers of the following formula, was designated Resin A2-4.

Synthetic Example 17 Synthesis of Resin A2-5

Monomer (a1-1-2), monomer (a1-5-1), monomer (a2-1-1), monomer (a3-2-3)and monomer (a3-1-1) were charged with molar ratio 30:14:6:20:30, anddioxane was added thereto in an amount equal to 1.5 weight times of thetotal amount of monomers to obtain a solution. Azobisisobutyronitrileand azobis(2,4-dimethylvaleronitrile) was added as an initiator theretoin an amount of 1 mol % and 3 mol % respectively with respect to theentire amount of monomers, and the resultant mixture was heated forabout 5 hours at 75° C. After that, the reaction solution was pouredinto a mixture of methanol and ion-exchanged water in large amounts toprecipitate a resin. The obtained resin was filtrated. Thus obtainedresin was dissolved in another dioxane to obtain a solution, and thesolution was poured into a large amount of a mixture of methanol andwater to precipitate a resin. The obtained resin was filtrated. Theseoperations were repeated two times for purification, resulting in 78%yield of copolymer having a weight average molecular weight of about7200. This copolymer, which had the structural units derived from themonomers of the following formula, was designated Resin A2-5.

Synthetic Example 18 Synthesis of Resin X1

Monomer (a1-1-1), monomer (a3-1-1) and monomer (a2-1-1) were mixed withmolar ratio 35:45:20, and dioxane was added thereto in an amount equalto 1.5 times by weight of the total amount of monomers to obtain asolution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile)was added as an initiator to obtain a solution in an amount of 1.0 mol %and 3.0 mol % respectively with respect to the entire amount ofmonomers, and the resultant mixture was heated for about 5 hours at 75°C. After that, the obtained reacted mixture was poured into a mixture ofa large amount of methanol and water to precipitate a resin. Theobtained resin was filtrated. Thus obtained resin was dissolved inanother dioxane to obtain a solution, and the solution was poured into amixture of methanol and water to precipitate a resin. The obtained resinwas filtrated. These operations were repeated 2 times for purification,resulting in a 75% yield of copolymer having a weight average molecularweight of about 7000. This copolymer, which had the structural units ofthe following formula, was referred to Resin X1.

Synthetic Example 19 Synthesis of Resin X2

Monomer (D) and monomer (a1-1-1) were mixed with molar ratio=80:20, anddioxane was added thereto in an amount equal to 1.5 times by weight ofthe total amount of monomers to obtain a solution.Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) was addedas an initiator to obtain a solution in an amount of 0.5 mol % and 1.5mol % respectively with respect to the entire amount of monomers, andthe resultant mixture was heated for about 5 hours at 70° C. After that,the obtained reacted mixture was poured into a mixture of a large amountof methanol and water to precipitate a resin. The obtained resin wasfiltrated. Thus obtained resin was dissolved in another dioxane toobtain a solution, and the solution was poured into a mixture ofmethanol and ion-exchanged water to precipitate a resin. The obtainedresin was filtrated. These operations were repeated 2 times, resultingin a 70% yield of copolymer having a weight average molecular weight ofabout 28000. This copolymer, which had the structural units of thefollowing formula, was referred to Resin X2.

(Preparing Resist Composition)

Resist compositions were prepared by mixing and dissolving each of thecomponents shown in Table 1, and then filtrating through a fluororesinfilter having 0.2 μm pore diameter.

TABLE 1 (Unit: parts) PB/PEB Basic ° C./ Resin Acid Generator Comp. ° C.Ex. 1 A1-1/A2-2 = 0.7/10 II1/B1 = 0.7/0.7 C1 = 0.07 110/105 2 A1-2/A2-1= 0.7/10 II1/B1 = 0.7/0.7 C1 = 0.07 95/85 3 A1-2/A2-2 = 0.7/10 II1/B1 =0.7/0.7 C1 = 0.07 110/105 4 A1-2/A2-3 = 0.7/10 II1/B1 = 0.7/0.7 C1 =0.07 110/105 5 A1-3/A2-2 = 0.7/10 II1/B1 = 0.7/0.7 C1 = 0.07 110/105 6A1-2/A2-2 = 0.7/10 I1 = 1.4 C1 = 0.07 110/105 7 A1-2/X1 = 0.3/10 II1/B1= 0.7/0.7 C1 = 0.07 110/105 8 A1-2/X1 = 0.3/10 I1/B2/B3 = C1 = 0.07110/105 0.5/0.5/0.1 9 A1-2/A2-4 = 0.7/10 II1/B1 = 0.7/0.7 C1 = 0.07110/105 10  A1-2/A2-5 = 0.7/10 II1/B1 = 0.7/0.7 C1 = 0.07 110/105 11 A1-4/A2-5 = 0.7/10 II1/B1 = 0.7/0.7 C1 = 0.07 110/105 12  A1-5/A2-5 =0.7/10 II1/B1 = 0.7/0.7 C1 = 0.07 110/105 13  A1-2/A2-5 = 0.7/10 II2/B1= 0.7/0.7 C1 = 0.07 110/105 Compar- ative Ex. 1 X2/X1 = 0.3/10 B2/B3 =1.0/0.1 C1 = 0.07 110/105<Resin>

Resins prepared by the Synthetic Examples

<Acid Generator>

II1: the salt represented by the formula (II-1)

II2: the salt represented by the formula (II-2)

B1: this was prepared by a method according to the method described inthe Examples of JP2010-152341A

B2: this was prepared by a method according to the method described inthe Examples of WO2008/99869 and JP2010-26478A

B3: this was prepared by a method according to the method described inthe Examples of JP2005-221721A

<Basic Compound: Qencher>

C1: 2,6-diisopropylaniline (obtained from Tokyo Chemical Industry Co.,LTD)

<Solvent of Resist Composition>

Propylene glycol monomethyl ether acetate 265 parts  Propylene glycolmonomethyl ether 20 parts 2-Heptanone 20 parts γ-butyrolactone 3.5parts (Producing Resist Pattern)

A composition for an organic antireflective film (“ARC-29”, by NissanChemical Co. Ltd.) was applied onto 12-inch silicon wafers and baked for60 seconds at 205° C. to form a 78 nm thick organic antireflective film.

The above resist compositions were then applied thereon by spin coatingso that the thickness of the resulting film became 110 nm after drying.

The obtained wafers were then pre-baked for 60 sec on a direct hot plateat the temperatures given in the “PB” column in Table 1 to obtain acomposition layer.

Line and space patterns were then exposed through stepwise changes inexposure quantity using an ArF excimer stepper for immersion lithography(“XT: 1900Gi” by ASML Ltd.: NA=1.35, ¾ Annular, X-Y deflection), on thewafers on which the composition layer thus been formed. The ultrapurewater was used for medium of immersion.

After the exposure, post-exposure baking was carried out by 60 secondsat the temperatures given in the “PEB” column in Table 1.

Then, puddle development was carried out with 2.38 wt %tetramethylammonium hydroxide aqueous solution for 60 seconds to obtaina resist pattern.

Effective sensitivity was represented as the exposure amount at which a50 nm line and space pattern resolved to 1:1 with the each resist film.

(Pattern Collapse (PCM) Evaluation)

Using a mask for forming 1:1 line and space pattern, a resist patternwas prepared at a higher exposure amount than the effective sensitivity,and observed obtained line pattern by the electron scanning microscope.

A “O” was given if the pattern was not observed to disappear due tocollapse or delamination when the line width was finer than 40 nm, and

a “X” was given if the pattern was observed to disappear due to collapseor delamination when the line width is 40 nm or more.

Table 2 illustrates there results. The parenthetical number meansminimum line width (nm) of resolved resist pattern.

(Evaluation of Defects)

The above resist compositions were applied on each of the12-inch-silicon wafers by spin coating so that the thickness of theresulting film became 150 nm after drying.

The obtained wafers were then pre-baked for 60 seconds on a direct hotplate at the temperatures given in the “PB” column in Table 1 to obtaina composition layer.

The thus obtained wafers with the produced composition layers wererinsed with water for 60 seconds using a developing apparatus (ACT-12,Tokyo electron Co. Ltd.).

Thereafter, the number of defects was counted using a defect inspectionapparatus (KLA-2360, KLA-Tencor Co. Ltd.)

Table 2 illustrates the results thereof.

TABLE 2 Ex. PCM Defects 1 ∘(37) 130 2 ∘(37) 160 3 ∘(36) 210 4 ∘(37) 2905 ∘(36) 190 6 ∘(34) 240 7 ∘(37) 330 8 ∘(38) 420 9 ∘(35) 180 10  ∘(34)160 11  ∘(35) 240 12  ∘(35) 280 13  ∘(33) 130 Com. Ex. 1 x(40) 720

According to the resin and the resist composition of the presentinvention, it is possible to achieve satisfactory less pattern collapsesand defects. Therefore, the present resist composition can be used forsemiconductor microfabrication.

What is claimed is:
 1. A resist composition comprising a resin having astructural unit represented by the formula (I), a resin being insolubleor poorly soluble in alkali aqueous solution, but becoming soluble in analkali aqueous solution by the action of an acid and not including thestructural unit represented by the formula (I), and an acid generatorrepresented by the formula (II),

wherein R¹ represents a hydrogen atom or a methyl group; A¹ represents aC₁ to C₆ alkanediyl group; A¹³ represents a C₁ to C₆ perfluoroalkanediyl group; X¹² represents *—CO—O— or *—O—CO—, * represents a bondto A¹³; A¹⁴ represents a C₁ to C₁₇ aliphatic hydrocarbon group thatoptionally has one or more halogen atoms;

wherein R²³ and R²⁴ independently represent a fluorine atom or a C₁ toC₆ perfluoroalkyl group; X²¹ represents an C₁ to C₁₇ divalent saturatedhydrocarbon group, one or more hydrogen atom contained in the divalentsaturated hydrocarbon group may be replaced by a fluorine atom, and oneor more —CH₂— contained in the divalent saturated hydrocarbon group maybe replaced by —O— or —CO—; R²⁵ represents a group having cyclic etherstructure; and Z¹⁺ represents an organic cation.
 2. The resistcomposition according to claim 1, wherein A¹ in the formula (I) is anethylene group.
 3. The resist composition according to claim 1, whereinX¹² in the formula (I) is *—CO—O—, * represents a bond to A¹³.
 4. Theresist composition according to claim 1, wherein A¹⁴ in the formula (I)is a cyclopropylmethyl, cyclopentyl, cyclohexyl, norbornyl or adamantylgroup.
 5. The resist composition according to claim 1, wherein R²⁵ inthe formula (II) is a group represented by the formula (IIA) or theformula (IIE).

wherein s1 represents an integer of 1 to 4, t1 represents an integer of0 to 2, provided that s1+t1 represents an integer of 1 to 4; s11represents an integer of 1 to 4, t11 represents an integer of 0 to 2;s12 represents an integer of 1 to 4, t12 represents an integer of 0 to2, provided that s12+t12 represents an integer of 0 to 4; R²⁶ in eachoccurrence represents a C₁ to C₁₂ saturated hydrocarbon group, a C₆ toC₁₈ aromatic hydrocarbon group, or two R²⁶ are bonded together to form aring, and one or more hydrogen atoms contained in the saturatedhydrocarbon group and the aromatic hydrocarbon group may be replaced bya C₁ to C₆ alkyl group or a nitro group, and one or more —CH₂— containedin the saturated hydrocarbon group and ring may be replaced by —O—; u1represents an integer of 0 to 8; R²⁷ and R²⁸ in each occurrenceindependently represent a hydroxy group, a halogen atom, a C₁ to C₆alkyl group, a C₁ to C₆ alkoxyl group, a C₁ to C₆ hydroxy alkyl group, aC₂ to C₇ acyl group, a C₂ to C₇ acyloxy group or a C₂ to C₇ acylaminogroup, or two of R²⁷ and R²⁸ may be bonded together to form a singlebond or a ring; u2 and u3 independently represent an integer of 0 to16; * represent a bond to X²¹.
 6. The resist composition according toclaim 1, which further comprises a solvent.
 7. A method for producing aresist pattern comprising steps of; (1) applying the resist compositionof claim 1 onto a substrate; (2) drying the applied composition to forma composition layer; (3) exposing the composition layer; (4) heating theexposed composition layer, and (5) developing the heated compositionlayer.